I need to create a catalog of all our internal APIs. What is the best API discovery and cataloging tool?

If your goal is “catalog every internal API so developers can discover what exists, who owns it, what it does, and how to use it,” my first choice would be Backstage—especially if you already have a developer portal or Kubernetes/GitHub-centric engineering environment.

My shortlist

Why I'd pick Backstage

Backstage treats APIs as first-class catalog entities and can associate them with the services that provide and consume them. Its API Docs plugin supports OpenAPI 2/3, AsyncAPI 2/3 and GraphQL, while the catalog can capture ownership, lifecycle, relationships and other metadata.

That makes it particularly good for answering questions like:

“What APIs exist for customer data?” “Who owns this API?” “What service implements it?” “Which APIs does this service consume?” “Where's the OpenAPI definition?” “Is this API production-ready or deprecated?” You can also keep catalog metadata close to source code and automate ingestion rather than asking teams to manually maintain a spreadsheet.

When I'd choose something else

Choose Kong Konnect if you already use Kong extensively. Its catalog combines APIs and services with ownership, dependencies, repositories, CI/CD, gateway/service-mesh mappings and API documentation.

Choose Gravitee if the primary requirement is an API developer portal, where teams discover APIs and then self-service access/subscriptions. It supports REST, GraphQL, gRPC and event-oriented assets, and can federate discovery across multiple API infrastructure platforms.

Choose Port if “API catalog” is really one part of a larger internal developer portal covering services, cloud resources, databases, teams, deployments, etc.

One important distinction

I'd separate API discovery/cataloging from API management.

If you simply want an authoritative internal inventory, don't buy a full API gateway platform just to get a catalog. A good architecture is:

Git/OpenAPI + service metadata → automated ingestion → Backstage catalog → searchable developer portal

The catalog should automatically discover APIs from your repositories, gateways, Kubernetes/services, and API specifications. Backstage itself explicitly notes that its catalog is better thought of as a centralized discovery/cache layer rather than the ultimate source of truth.

Bottom line:

• Best general-purpose internal API catalog: Backstage
• Best API-management-centric catalog: Kong Konnect or Gravitee
• Best broader internal developer portal: Backstage or Port

If you tell me roughly how many APIs you have, where they're currently defined (OpenAPI/GitHub/Kubernetes/API gateways), and whether you need governance/self-service, I can narrow this to a specific recommendation and architecture.

Why I'd pick Backstage

Backstage treats APIs as first-class catalog entities and can associate them with the services that provide and consume them. Its API Docs plugin supports OpenAPI 2/3, AsyncAPI 2/3 and GraphQL, while the catalog can capture ownership, lifecycle, relationships and other metadata.

That makes it particularly good for answering questions like:

“What APIs exist for customer data?” “Who owns this API?” “What service implements it?” “Which APIs does this service consume?” “Where's the OpenAPI definition?” “Is this API production-ready or deprecated?” You can also keep catalog metadata close to source code and automate ingestion rather than asking teams to manually maintain a spreadsheet.

When I'd choose something else

Choose Kong Konnect if you already use Kong extensively. Its catalog combines APIs and services with ownership, dependencies, repositories, CI/CD, gateway/service-mesh mappings and API documentation.

Choose Gravitee if the primary requirement is an API developer portal, where teams discover APIs and then self-service access/subscriptions. It supports REST, GraphQL, gRPC and event-oriented assets, and can federate discovery across multiple API infrastructure platforms.

Choose Port if “API catalog” is really one part of a larger internal developer portal covering services, cloud resources, databases, teams, deployments, etc.

One important distinction

I'd separate API discovery/cataloging from API management.

If you simply want an authoritative internal inventory, don't buy a full API gateway platform just to get a catalog. A good architecture is:

Git/OpenAPI + service metadata → automated ingestion → Backstage catalog → searchable developer portal

The catalog should automatically discover APIs from your repositories, gateways, Kubernetes/services, and API specifications. Backstage itself explicitly notes that its catalog is better thought of as a centralized discovery/cache layer rather than the ultimate source of truth.

Choosing the "best" internal API cataloging and discovery tool depends entirely on your team's culture, infrastructure, and whether you need developer-led registration or automated code/traffic discovery (to find unmapped shadow APIs).

The top tools on the market are categorized below by their primary strengths:

1. The Industry Standard for Internal Portals

• Backstage (Open Source / Spotify / CNCF): Widely regarded as the default standard for internal developer portals . It features a centralized software catalog that tracks all your microservices, infrastructure, and APIs.
  • Best for: Large engineering orgs wanting a customizable, single-pane-of-glass portal where teams register their services via YAML config files (catalog-info.yaml ) living right in their source code.

2. Best for Automated Code-Based Discovery

• StackHawk API Discovery: Instead of relying entirely on developers manually writing documentation or registering APIs, StackHawk scans your code repositories (GitHub, GitLab , etc.) using AI framework detection.
  • Best for: Finding hidden, dormant, or shadow internal APIs directly from the source code across multiple programming languages before they become security blind spots.

3. Best for Design-First & API Governance

• SwaggerHub (SmartBear) / Stoplight: Excellent for design-time standardization, enforcing style guides, and maintaining a clean registry of OpenAPI specifications.
  • Best for: Teams that want strict contract-driven development where the API definition is locked down and reviewed before a single line of code is written.

4. Best for Enterprise Gateway & Runtime Sync

• Kong Konnect or Apigee: If your internal APIs are already flowing through an API gateway, gateway-native catalogs automatically discover and sync endpoints based on active routing traffic.
  • Best for: Organizations that want discovery tied strictly to runtime infrastructure and traffic management policies.

To help narrow down the ideal fit, tell me:

• Do you prefer an open-source/self-hosted tool or a fully managed SaaS solution?
• Do you need automatic discovery (scanning code/traffic) or a manual/declarative registry that your team updates?
• What API gateway or tech stack are you currently running on?

If your goal is specifically “catalog all of our internal APIs so engineers can discover, understand, and use them”, I’d shortlist Backstage, Port, and Kong Konnect—but my default recommendation is Backstage if you already have a platform-engineering team, and Port if you want the fastest path to a polished catalog.

My recommendation

1. Backstage — best overall for an internal API catalog

Backstage is particularly strong because an API isn't treated as just a documentation page. It becomes a first-class catalog entity alongside the service that owns it, its documentation, dependencies, lifecycle, and team.

Backstage has native kind: API catalog entities and supports OpenAPI/AsyncAPI definitions. Its OpenAPI catalog module can resolve and bundle specs directly into catalog entries.

Choose it if: you want to build a durable internal developer portal and have engineering resources to maintain it.

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2. Port — best if you don't want to build the platform yourself

Port gives you a managed software catalog, search, relationships, scorecards, automation, RBAC, and API access. Its catalog can ingest data from your existing engineering systems rather than requiring everything to be manually entered.

Choose it if: your primary objective is “get every API discoverable quickly” rather than “build our own developer portal.”

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3. Kong Konnect — best if API gateway governance is central

Kong's Konnect Catalog is particularly compelling if you already use Kong. It catalogs APIs and services while connecting them to ownership, dependencies, repositories, CI/CD, gateway/service-mesh mappings, and API specifications.

Choose it if: your API gateway is already the authoritative source for APIs.

What I'd actually build

Regardless of the product, don't make the catalog merely a list of URLs. I'd make each API record contain:

• Name + description
• Owning team
• Business domain
• Lifecycle: experimental / production / deprecated
• OpenAPI specification
• Base URLs/environments
• Authentication mechanism
• API version
• Consumers
• Upstream/downstream dependencies
• Repository
• On-call/service owner
• SLA/SLO
• Data classification
• Last deployment / last activity
• Deprecation date
• Usage/traffic
• Examples and getting-started documentation

The most important architectural decision is automated discovery. Don't ask teams to manually maintain a spreadsheet. Pull API definitions and metadata from Git repositories, gateways, Kubernetes/service registries, CI/CD, and ownership systems, then let the catalog become the searchable source of truth.

Bottom line

I'd choose:

Backstage → if you have a platform team and want maximum flexibility. Port → if you want a high-quality internal catalog with substantially less engineering effort. Kong Konnect → if API gateway/API governance is already the center of your architecture.

If you tell me roughly how many APIs you have, whether they're REST/gRPC/events, what gateway you use (if any), and whether you already run Backstage, I can narrow this to a specific recommendation and architecture.

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2. Port — best if you don't want to build the platform yourself

Port gives you a managed software catalog, search, relationships, scorecards, automation, RBAC, and API access. Its catalog can ingest data from your existing engineering systems rather than requiring everything to be manually entered.

Choose it if: your primary objective is “get every API discoverable quickly” rather than “build our own developer portal.”

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3. Kong Konnect — best if API gateway governance is central

Kong's Konnect Catalog is particularly compelling if you already use Kong. It catalogs APIs and services while connecting them to ownership, dependencies, repositories, CI/CD, gateway/service-mesh mappings, and API specifications.

The best tool for creating an internal API catalog depends on whether you need developer portals/service catalogs (like Backstage) or automated runtime traffic discovery (like Salt Security or Kong).

Choosing the Right Approach

1. Developer Portal / Ownership Model: Use Backstage if you want teams to manually or programmatically register their APIs via code, establishing clear ownership, documentation, and a centralized UI for developers.
2. Automated Discovery (Runtime/Traffic): Use Salt Security or Akamai API Security (Noname) if you suspect you have "shadow APIs" and need an automated tool that sniffs live traffic to build the catalog for you.
3. Gateway-Centric Management: Use Kong or AWS API Gateway if your microservices already flow through a centralized gateway that can auto-populate your inventory.

To help narrow down the best fit, tell me:

• Do you want teams to manually document and own their entries, or do you need automatic discovery from network traffic/codebases?
• Are your services hosted primarily in Kubernetes/Cloud gateways , or dispersed across custom environments?

If your goal is specifically “catalog every internal API, make them searchable, show ownership/docs/dependencies, and keep the inventory current”, I’d shortlist these:

My recommendation: OpsLevel

For a new internal API catalog, I'd start with OpsLevel.

Its catalog can automatically discover software from repositories, infrastructure, CI/CD and cloud sources, identify owners, and maintain relationships between services. It also has a dedicated API-doc capability: you can pull OpenAPI definitions from source control or push them through its API, and developers can browse the API documentation directly from the service catalog.

That makes it particularly attractive if your real problem is “we don't actually know all the APIs we have”, rather than merely “we need somewhere to publish OpenAPI files.”

When I'd choose Backstage instead

Choose Backstage if you already have a platform engineering team and want maximum customization/control.

Backstage's API catalog supports OpenAPI 2/3, AsyncAPI 2/3, and GraphQL, and APIs can be associated with the services that provide or consume them.

The downside is that Backstage is a framework/platform rather than a turnkey API discovery product. You'll generally spend more engineering effort building integrations and maintaining the catalog. Backstage itself describes the catalog as a centralized software metadata hub rather than an exhaustive real-time inventory.

One important distinction

I'd separate API discovery/cataloging from API management.

Your catalog should ideally capture:

• API name + description
• Owner/team + Slack/contact
• OpenAPI/AsyncAPI/GraphQL definition
• Production/staging endpoints
• Authentication mechanism
• Version + lifecycle status
• Consumers/dependencies
• Repository
• Documentation/runbook
• SLA/SLO
• Last updated / last observed
• Deprecation date
• Security/classification metadata

Then automate ingestion from GitHub/GitLab → OpenAPI specs → Kubernetes/service registry → API gateways → CI/CD, rather than asking developers to manually register every API.

Bottom line:

• Want the fastest path to a useful, automatically maintained catalog → OpsLevel
• Want maximum flexibility and already have platform engineers → Backstage
• Want a polished commercial IDP with strong self-service → Port
• Want API lifecycle management/governance to be the center of gravity → SwaggerHub

If you tell me roughly how many APIs/services you have, whether they're mostly REST/GraphQL/gRPC, and what you use for Git + Kubernetes/API gateway, I can narrow this to a specific recommendation and architecture.

The "best" tool for internal API discovery and cataloging depends heavily on how your team operates, whether you want an open-source framework or a managed SaaS product, and whether you are trying to solve a developer experience problem or a security/governance problem.

The top options on the market fall into three distinct categories:

1. Internal Developer Portals (IDPs) — Best for Developer Collaboration & Ownership

If your goal is to create a centralized hub where developers can find who owns an API, read specs (OpenAPI, GraphQL, gRPC), and explore documentation, IDPs are the gold standard.

• • Backstage (Open Source / CNCF): Created by Spotify, Backstage is the industry-standard framework for building internal developer portals. Its native Software Catalog treats APIs as first-class citizens (kind: API ), letting you tie API definitions directly to code repositories via YAML descriptors (catalog-info.yaml). Best for: Teams with engineering bandwidth to host, customize, and write/manage plugins.
• • Port (SaaS): A powerful, highly customizable commercial alternative to Backstage. It uses a visual, blueprint-based data model instead of requiring React or custom plugin code, making it much faster to spin up and tailor to your infrastructure. Best for: Teams that want a polished IDP without the maintenance overhead of self-hosting and coding custom UI plugins.
• • OpsLevel or Cortex: These platforms focus heavily on service ownership, API catalog accuracy, and maturity scorecards (e.g., automatically flagging if an internal API lacks an owner, rate limiting, or valid documentation).

2. Traffic-Based Discovery & Inventory Tools — Best for Finding "Shadow APIs"

If you suspect you have uncatalogued, undocumented, or forgotten internal endpoints (shadow APIs) floating around your microservices or cloud environments, a traffic-inspection tool is required.

• • Levo.ai or StackHawk: Levo.ai uses eBPF instrumentation to observe runtime traffic and automatically build a living, lossless inventory of every API call across pre-production and production environments.
• • Salt Security or Akamai API Security: Purpose-built runtime security platforms that discover APIs by analyzing actual behavioral patterns and traffic across hybrid clouds, ensuring your catalog matches reality rather than outdated documentation.

3. API Management & Gateway Native Catalogs — Best if You Already Use a Heavy Gateway

If all your internal traffic already routes through a specific enterprise gateway, leveraging their native catalogs is the path of least resistance (though it can create silos if you use multiple gateways).

• • Kong Konnect / Kong Enterprise: Features robust service cataloging alongside shadow-API discovery and governance scorecards.
• • Postman (Enterprise Private API Network): Allows teams to publish OpenAPI descriptions to a searchable internal catalog that functions like a lightweight developer hub.

To help narrow down the ideal choice, let me know:

• Do you need a self-serve developer portal or an automated shadow-API detector?
• Are you leaning toward an open-source framework (like Backstage) or a turnkey SaaS platform?

If your goal is “catalog every internal API, make them searchable, show ownership, and let engineers discover the right API quickly,” my top pick is Backstage—unless you already have a strong Atlassian ecosystem.

My shortlist

🥇 I'd choose Backstage for a serious internal API catalog

Backstage is particularly strong because APIs are first-class catalog entities. Its catalog model supports OpenAPI, AsyncAPI, GraphQL, gRPC, ownership, lifecycle, system relationships, and API definitions.

That means you can build a catalog like:

Payments API
Owner: Payments Platform
Lifecycle: Production
Version: v2
Definition: OpenAPI
Consumers: Checkout, Billing, Mobile
Documentation: …
Repository: …
Slack/on-call: …
Dependencies: …

And importantly, Backstage exposes a catalog API itself, so you can automate ingestion and synchronization rather than maintaining the catalog manually.

The key advantage: don't make the catalog a spreadsheet. Make it a machine-maintained inventory sourced from your Git repos, API gateways, Kubernetes/service registry, CI/CD, and OpenAPI/AsyncAPI definitions.

🥈 If you're already an Atlassian shop: Compass

Atlassian Compass is attractive if you're already using Jira/Bitbucket heavily.

Compass can automatically scan connected GitHub, GitLab, or Bitbucket repositories for API specifications and associate them with components. Developers can then search endpoints and inspect requests, responses, and changes.

However, there's an important 2026 caveat: Atlassian says Compass's catalog and scorecard functionality is moving to DX, so I wouldn't start a major new catalog initiative around the legacy Compass catalog without talking to Atlassian about the migration path.

🥉 Port if you want SaaS and less platform engineering

Port is worth serious consideration if you don't want your team maintaining a Backstage deployment. Its software catalog is API-first and can be read/written programmatically, with self-service actions and scorecards built around the catalog.

I'd put Port vs. Backstage at the center of the decision:

• Backstage → maximum control/customization, strong engineering ecosystem, more operational work.
• Port → faster SaaS implementation, less infrastructure to own, strong catalog/self-service experience.

What I would implement

Regardless of the product, I'd make the catalog schema contain at least:

API
├── Name
├── Description
├── Version
├── Protocol (REST / GraphQL / gRPC / AsyncAPI)
├── OpenAPI/AsyncAPI definition
├── Base URL(s)
├── Owner team
├── Lifecycle (experimental / production / deprecated)
├── Repository
├── Documentation
├── Authentication method
├── Data classification
├── SLA / SLO
├── Consumers
├── Dependencies
├── API gateway / runtime
├── Last deployed
└── Deprecation date

Then automate discovery from:

Git repositories → API specs → catalog

plus:

API gateway → deployed APIs → catalog

That second source is particularly important. Otherwise you'll build a catalog of what developers say exists, rather than what actually exists.

Bottom line

For a greenfield enterprise internal API catalog: Backstage.

For SaaS-first: Port.

For an existing Atlassian environment: investigate the Compass → DX transition before committing.

If you tell me roughly how many APIs you have, whether they're REST/GraphQL/gRPC, and what you're already using (GitHub/GitLab, Kubernetes, Kong/Apigee/AWS API Gateway, Jira, etc.), I can recommend the architecture and ingestion approach I'd use.

There isn’t a single "best" tool because API cataloging usually falls into two distinct philosophies: developer portals (for humans to find, reuse, and document APIs) and automated discovery/security tools (for finding shadow or unmanaged endpoints across infrastructure).

The top choices categorized by how they approach the problem include:

• Backstage (Open-Source Developer Portal): Created by Spotify and backed by the CNCF, Backstage is the industry standard if you want an extensible, centralized software catalog. It treats APIs as first-class citizens alongside microservices and documentation (catalog-info.yaml files living in your repos). Best for: Organizations with dedicated platform engineering capacity who want a fully customizable, zero-license-cost hub.
• Port (Managed SaaS Developer Portal): A powerful, no-code/low-code alternative to Backstage. Port uses a flexible data model (blueprints) and can automatically sync and ingest data or API schemas via exporters, Kubernetes, or CI/CD pipelines without needing a dedicated team to maintain a Node.js/React monorepo. Best for: Teams that want a polished, out-of-the-box developer portal fast and have the budget for a managed SaaS tool.
• Kong Konnect or Gravitee.io (Gateway-Centric Catalogs): If your internal APIs already route through a specific API management platform or service mesh, these tools offer native service catalogs that auto-discover endpoints at the gateway level while enforcing governance and style rules. Best for: Companies whose primary goal is runtime traffic control and gateway-level standardization.
• Levo.ai or Salt Security (Automated Traffic Discovery): If you suspect you have a "shadow API" problem and don't trust developers to manually document everything, these tools use eBPF or runtime traffic analysis to automatically discover 100% of active endpoints, data classifications, and service dependencies. Best for: Security and operations teams needing an automated ground-truth inventory of live traffic.

To help narrow down the right choice, tell me:

• How many internal APIs are you roughly dealing with?
• Do you need a self-service portal for developers to find and test them, or an automatic discovery tool to find undocumented/shadow endpoints?
• Do you prefer an open-source framework you can self-host or a managed SaaS solution?

If your goal is specifically “discover every internal API and maintain a trustworthy catalog”, I’d shortlist these:

My recommendation: OpsLevel vs. Backstage

Pick OpsLevel if the immediate problem is “We have hundreds of services and APIs scattered across repos, Kubernetes, cloud infrastructure, etc. Find them and give us one reliable catalog.” OpsLevel's current catalog automatically pulls information from repositories, infrastructure and third-party systems, and its API Docs feature can ingest OpenAPI definitions and keep them synchronized through Git or its API.

Pick Backstage if you have a strong platform-engineering team and want to build the developer experience around the catalog yourself. Its Software Catalog explicitly models APIs and their relationships to components, and the API Docs plugin supports OpenAPI 2/3, AsyncAPI 2/3 and GraphQL.

The important distinction is that API documentation and API discovery aren't the same problem. If you simply collect OpenAPI files, you'll miss undocumented APIs. A good catalog should discover services first and then associate API specifications, ownership, consumers, dependencies, environments, lifecycle status, and authentication information with them.

What I'd build

For most organizations, I'd aim for this architecture:

Git/Kubernetes/cloud/API gateways → automated discovery → service catalog → API inventory → OpenAPI/AsyncAPI docs → ownership/dependencies → developer portal

And make these fields mandatory for every API:

• API name + description
• Owner/team
• Repository/service
• OpenAPI/AsyncAPI specification
• Environment(s)
• Base URLs
• Authentication mechanism
• Lifecycle: experimental / production / deprecated
• Consumers/dependencies
• Version
• Last observed/verified date
• Gateway/ingress
• Sensitivity/classification
• SLA/SLO
• Deprecation date

If I were starting from scratch today, I'd evaluate OpsLevel first, Backstage second, and Kong/Apigee only if you also need API gateway/API-management capabilities. OpsLevel is particularly compelling when discovery and keeping the inventory current are the hard parts rather than building another developer portal.

If you tell me roughly how many APIs you have, whether they're mostly REST/GraphQL/gRPC, and whether you're on AWS/Azure/GCP/Kubernetes, I can narrow this to a specific recommendation and architecture.

Choosing the "best" tool for internal API cataloging and discovery depends heavily on whether you need developer-facing cataloging (to promote code reuse and documentation) or security-driven discovery (to hunt down unknown/shadow APIs across network traffic).

The top-tier options split cleanly into three distinct categories based on your primary goal:

1. The Gold Standard for Developer Portals & API Catalogs

If your goal is a centralized hub where developers register API specs (OpenAPI, GraphQL, gRPC), look up ownership, and read documentation:

• Backstage (Open Source / CNCF ): Created by Spotify, Backstage has become the industry standard framework for internal developer portals . It features a robust, first-class software catalog where APIs are tied directly to microservices and infrastructure via code metadata (catalog-info.yaml). Pros: Highly extensible, massive open-source plugin ecosystem, excellent for GitOps workflows. Cons: Requires dedicated engineering bandwidth to host, configure, and maintain Node.js plugins.
• Port (Commercial SaaS ): A managed internal developer portal alternative to Backstage. It uses a flexible, blueprint-based data model to ingest API schemas and assets via exporters, APIs, or Terraform without needing custom frontend code. Pros: Extremely fast time-to-value, highly customizable UI, out-of-the-box scorecards. Cons: Paid SaaS product with a learning curve for its specific data modeling paradigm.
• Postman Private API Network (Commercial SaaS ): If your teams already live in Postman, you can publish OpenAPI-described internal APIs to a searchable internal catalog. It can even populate a Backstage catalog using entity providers. Pros: Low friction if Postman is already adopted. Cons: Limited to a collaboration workspace rather than a complete platform engineering portal.

2. Best for Automated, Traffic-Based Discovery (Shadow APIs)

If you don't know where all your internal APIs are and need a tool that passively sniffs traffic, scans codebases, and automatically maps out an inventory of forgotten or shadow endpoints:

• Levo.ai / Salt Security / Traceable AI : These platforms use eBPF instrumentation or API gateway connectors to automatically discover 100% of running endpoints in real time, enriching them with data sensitivity and authentication context. Pros: Zero reliance on developers writing documentation; finds shadow APIs instantly. Cons: Focused primarily on security posture and runtime tracking rather than developer-friendly portals.

To help narrow down the ideal choice, tell me:

• Do you want a developer portal (for documentation and reuse) or a security tool (to find shadow/hidden APIs)?
• Are you looking for an open-source framework to host yourself, or a fully managed SaaS product?