We use a headless CMS. Who offers a translation management system that syncs content back and forth via API?

Several major Translation Management Systems (TMS) specialize in API-first, bi-directional syncing with headless architectures . They pull structured content (JSON/fields) from your CMS, route it through translation workflows (human or AI), and push the localized content back automatically.

Leading TMS options with robust headless CMS integrations include:

• Crowdin : Highly developer-friendly with robust API/CLI support and extensive out-of-the-box apps for headless platforms like Contentful, Storyblok, Strapi, and Hygraph. It handles continuous localization well and allows content to sync bi-directionally via automated webhooks.
• Smartling : An enterprise-grade TMS offering sophisticated, native connectors for popular headless platforms (such as Contentstack and Storyblok). It features visual context rendering, automated asset tracking, and deep workflow automation.
• Phrase : Formerly Memsource, Phrase provides an agile localization platform with robust APIs and a flexible Global Technology Ecosystem that connects cleanly with modern headless and decoupled CMS environments.
• Lokalise : Known for speed and modern UI, Lokalise offers strong API-driven integrations, webhooks, and automation capabilities suited for sync-heavy engineering and localization teams working with structured content.

To help narrow down the best fit, tell me:

• Which headless CMS are you currently using (e.g., Contentful, Strapi, Sanity, Contentstack)?
• Do you prefer a fully native app marketplace integration or building a custom webhook/API pipeline?

Yes. Several TMS/localization platforms are designed for exactly this API-based, bidirectional workflow: pull translatable content from your headless CMS → manage/translate it → push the localized content back into the CMS.

Strong options

• Smartling — Probably the strongest enterprise-oriented option. Its REST API supports uploading source content, managing translation jobs, and downloading completed translations; it also supports webhooks for event-driven updates. Smartling explicitly supports custom integrations for CMSs where a native connector doesn't exist.
• Lokalise — Very API-centric and particularly good if your CMS content is structured/JSON-heavy. Its API supports pulling content from external systems, webhooks for changes, and automatically pushing completed translations back to the source system.
• Crowdin — Good for continuous localization and developer-oriented workflows. It has APIs plus CMS integrations; for example, its Contentful integration supports both syncing source content into Crowdin and pushing translations back, including automatic synchronization.
• Phrase — Another major TMS worth evaluating, especially if you want translation memory, terminology management, automated workflows, and APIs around a broader localization program.
• TransPerfect / GlobalLink — More enterprise/agency-oriented, with APIs and integrations suitable for organizations that want the TMS tightly integrated into their existing localization operation.

The important distinction

If your CMS is something like Contentful, Contentstack, Sanity, Storyblok, Strapi, Hygraph, Prismic, or DatoCMS, I'd specifically look for a vendor that can handle:

1. CMS → TMS: detect new/changed fields and send them automatically.
2. TMS workflow: translation memory, glossary, human/AI translation, review, etc.
3. TMS → CMS: write approved translations back into the correct localized fields/entries.
4. Webhooks: notify your integration when translation status changes.
5. Structured content: preserve references, rich text, arrays, nested objects, etc., rather than treating everything as a flat document.

Smartling, for example, explicitly describes this kind of custom integration as automating the full lifecycle from content upload through delivery of completed translations.

If you tell me which headless CMS you're using, I can narrow this to the 3–4 TMS vendors with the best actual integration for that CMS, including whether the sync is truly bidirectional, webhook-driven, and field/JSON aware.

Several leading Translation Management Systems (TMS) specialize in API-first, bi-directional syncing with headless CMS platforms (such as Contentful, Strapi, Storyblok, DatoCMS, and Contentstack). Instead of exporting XLIFF or JSON files manually, these tools pull field-level content, route it through your translation workflow (human, machine, or AI), and push the translated entries straight back into your CMS.

Top TMS providers with robust, bi-directional headless CMS integrations include:

1. Crowdin – Excellent for developer-heavy workflows and continuous localization. They feature native apps and robust APIs for major headless systems (like Contentful, DatoCMS, and Strapi), allowing you to sync structured fields automatically while skipping layout or technical config fields.
2. Phrase (incorporating Phrase TMS and Phrase Strings) – Highly agile and built for automated CI/CD and API-first pipelines. It handles software strings as well as structured marketing and document content within a unified asset layer (translation memory, glossaries, and AI).
3. Smartling – An enterprise-grade TMS that offers sophisticated visual context tools alongside automated API connectors. It syncs content back and forth dynamically, which is ideal if you have large-scale content operations requiring rigorous quality scoring and vendor management.
4. Lokalise – Known for speed and modern developer workflows. While heavily adopted for digital products and app localization, Lokalise features strong webhook and API architectures to handle content sync across decoupled and headless web properties.
5. Translated (TranslationOS) – An AI-first localization ecosystem that provides programmatic API infrastructure to connect headless architectures (like Contentful) directly to continuous translation loops without manual handoffs.

If you share which specific headless CMS you are using (e.g., Contentful, Strapi, Storyblok) and your preferred translation workflow (pure AI/machine vs. human linguists), I can give you a more precise recommendation on which integration fits best.

Yes. For a headless CMS, you’ll want a TMS that can pull structured content through an API, manage translation workflows, and push the translated content back into the CMS.

A few strong options:

• Smartling — Probably the strongest fit if you want an API-first/custom integration. Its REST API supports uploading source content, managing translation jobs, retrieving completed translations, and webhooks for near-real-time events. Smartling explicitly supports custom integrations for CMSs without a prebuilt connector.
• Lokalise — Very API-centric, with REST APIs and webhooks. It specifically describes the workflow as pulling content from your CMS, triggering localization when source content changes, and pushing finished translations back automatically. It also has integrations for headless CMSs such as Contentful and Contentstack.
• Phrase — Another major TMS worth evaluating, particularly for larger localization programs. It has APIs and integrations designed to connect translation workflows to development/content systems.
• TransPerfect — More enterprise/managed-service oriented. Worth considering if you want the TMS plus professional translation resources rather than simply providing a platform for your existing translators.

What I'd shortlist

If your requirement is specifically “headless CMS ↔ API ↔ TMS ↔ API ↔ headless CMS”, I'd start with Smartling and Lokalise.

| Smartling | Lokalise --- | --- | --- REST API | Strong | Strong Webhooks | Yes | Yes Custom headless-CMS integration | Yes | Yes Push translations back | Yes | Yes Prebuilt headless CMS integrations | Several | Several Good for developer-built integration | Excellent | Excellent Translation-management features | Very strong | Very strong

Smartling has particularly explicit support for the bidirectional pattern you're describing: its documentation says APIs can be used to send content to the TMS and retrieve translated content, while webhooks can notify your CMS when work is complete.

If you tell me which headless CMS you're using (Contentful, Contentstack, Sanity, Storyblok, Strapi, Hygraph, custom, etc.), I can narrow this down to the 3–5 TMS vendors that actually integrate with it, including how the sync works and approximate pricing.

Several top-tier translation management systems (TMS) and localization platforms provide robust, API-first integrations designed to sync content back and forth with a headless CMS (such as Contentful, Contentstack, or Strapi). These platforms use webhooks and field-level API connectors to automatically detect updates, route text for human or AI translation, and write localized variants directly back to the correct fields in the CMS.

• Smartling : Offers automated, API-based connectors built specifically for headless architectures, featuring visual context capture and continuous localization pipelines that sync content updates instantly.
• Crowdin : Provides a comprehensive Crowdin Store with app connectors for headless systems, parsing structured JSON/Markdown fields via API and pushing approved translations straight back to target language fields or folders.
• Lokalise : Delivers powerful API and webhook integrations tailored for headless platforms like Contentful, allowing teams to automate sync tasks and manage translation workflows seamlessly.
• Phrase : Features robust developer-focused toolsets (like Phrase Strings) with deep API integrations for headless CMS ecosystems to manage locale-specific content updates programmatically.
• Translated (TranslationOS) : Utilizes event-driven webhooks and its TranslationOS infrastructure to pull field content from headless setups, run AI/human hybrid workflows, and write translations back via callback APIs.

If you want, tell me:

• Which headless CMS you are currently using
• Whether you prefer AI translation, human review, or a hybrid approach

I can help you pinpoint the best integration fit for your tech stack.

Yes. If your requirement is a headless CMS ↔ TMS bidirectional sync over API, there are several strong options.

My shortlist

1. Lokalise — probably where I'd start. Its API is explicitly designed to connect localization to other systems: content can be pulled from a CMS, changes can trigger localization via webhooks, and completed translations can be pushed back automatically.

2. Phrase — particularly compelling if you need enterprise-grade translation memory, terminology, QA, approvals, and governance. Phrase exposes APIs specifically for integrating with CMSs and other third-party systems.

3. Smartling — worth considering if you're looking for a more managed enterprise localization operation and want connectors rather than building everything yourself.

4. Crowdin — a good option when your engineering team wants API/webhook/CI/CD control over localization.

The architecture you're describing is essentially:

Headless CMS → API/webhook → TMS → translation/review → API/webhook → Headless CMS

That's a well-supported pattern. For example, Translated documents exactly this kind of round-trip workflow: CMS changes initiate translation through its API, then a webhook delivers the completed translation so your application can update the CMS.

One important distinction: if your CMS isn't one of the vendors' prebuilt integrations, I'd prioritize a TMS with a good generic REST API + webhooks, rather than choosing based solely on its list of native CMS connectors.

If you tell me which headless CMS you're using (Contentful, Contentstack, Sanity, Strapi, Hygraph, Storyblok, a custom CMS, etc.), I can narrow this down to the 2–3 TMSs that provide the cleanest two-way integration, including what fields/content structures they can sync.

Yes. For a headless CMS, you typically want a translation management system (TMS) with API-based, bidirectional sync: CMS → TMS for translation, then TMS → CMS to write localized content back into the correct fields/locales. The strongest options are:

A typical architecture looks like:

Headless CMS
(Contentful / Sanity / Strapi / Contentstack / custom)
        |
        | API + webhook
        v
Translation Management System
        |
        | translation memory + MT + human review
        v
TMS pushes localized fields back
        |
        v
Headless CMS locale entries

How I’d shortlist them

• Best general choice for headless CMS: Lokalise
  Good balance of API maturity, developer tooling, and CMS integrations.

• Best enterprise choice: Smartling or Phrase
  Better if you need vendor translation workflows, approvals, QA, terminology management, and governance.

• Best continuous localization workflow: Crowdin or Transifex
  Strong when content changes frequently and you want automated sync triggered by commits, webhooks, or CMS changes.

The exact winner depends heavily on your CMS. For example, Contentful, Sanity, Strapi, Contentstack, Hygraph, and a custom GraphQL CMS each have different connector maturity.

If you tell me:

1. which headless CMS you use,
2. number of languages, and
3. whether translations are human, machine, or hybrid,

I can narrow it to the best 2–3 options.

Several major Translation Management Systems (TMS) specialize in headless architecture, offering robust, bi-directional API and webhook syncs with popular headless CMS platforms (such as Contentful, Contentstack, Hygraph, Storyblok, and Sanity).

The leading platforms offering bi-directional API content synchronization include:

• Smartling : Provides native, pre-built API connectors tailored for enterprise headless stacks like Contentful and Contentstack. It automatically detects content updates in your CMS, routes them through translation workflows (AI, machine, or human), and writes the finished localized content directly back to the CMS without manual file manipulation.
• Crowdin : Offers robust field-level and entry-level localization integrations designed for headless environments (e.g., Hygraph, DatoCMS, and ButterCMS). Changes made to source fields in the CMS automatically push to Crowdin via API, and approved translations sync back seamlessly.
• Lokalise : Highly optimized for continuous localization, featuring deep apps and API connectors for headless and decoupled CMS platforms including Contentful, Contentstack, Storyblok, and Hygraph. It allows you to trigger automated bulk imports/exports and manage locales programmatically via robust REST APIs and webhooks.
• Phrase : (Combining Phrase Strings and Phrase TMS) delivers strong API-first design, CI/CD integrations, and automated content connectors that pull and push structured field data across modern technical and marketing stacks.

If you share which specific headless CMS you are currently using (e.g., Contentful, Sanity, Storyblok) and your preferred translation workflow (fully automated AI vs. human agency review), I can point you toward the most seamless integration configuration for your stack.

Yes. If your requirement is essentially “headless CMS → TMS via API → translation workflow → translated content back into the CMS”, several vendors fit.

Strong options

Smartling and Lokalise are probably the first two I'd evaluate for a headless-CMS architecture. Smartling specifically documents using its API to automate translation for a custom content management system, while its API supports submitting content and retrieving completed translations.

Lokalise is particularly explicit about the bidirectional workflow: content can be pulled from a CMS, changes can trigger localization automatically via webhooks, and completed translations can be pushed back to the source system automatically. It also offers a substantial REST API.

For example, with Contentful, Lokalise already has a native integration that syncs Contentful content with Lokalise. docs.lokalise.com Smartling likewise has integrations plus APIs for cases where your particular CMS doesn't have a prebuilt connector.

The architecture I'd look for

Headless CMS
     │
     │ API / webhook
     ▼
Translation Management System
     │
     ├── Translation memory
     ├── Glossary / terminology
     ├── Machine translation
     └── Human translation / review
     │
     │ API / webhook
     ▼
Headless CMS
     │
     ▼
Localized frontend

The important distinction is that you want a TMS with an integration/API layer, rather than merely a translation API such as Google Translate or DeepL. The TMS should retain translation memory, workflow/status, linguistic assets, and ideally be able to notify your CMS when a translation is complete.

If you tell me which headless CMS you're using (Sanity, Contentful, Strapi, Storyblok, DatoCMS, Prismic, etc.), I can narrow this to the 3–5 TMSs that have the cleanest integration with it, including whether the sync is truly bidirectional and how the API workflow works.

Several major Translation Management Systems (TMS) and localization platforms provide robust, API-driven connectors designed to sync content back and forth with headless CMSs (such as Contentful, Contentstack, Sanity, Storyblok, and Strapi).

The leading TMS options that automate bi-directional content synchronization via API include:

• Smartling : Offers enterprise-grade, pre-built API connectors specifically for headless platforms like Contentful, Contentstack, and Sanity. It automatically detects new or updated fields in your CMS, routes them through translation workflows, and writes the translated strings back without manual file export/import.
• Crowdin : Features comprehensive API support and dedicated apps for various headless architectures (such as ButterCMS and Contentful). It extracts translatable text payloads while ignoring structural configuration, then syncs the localized content back programmatically.
• Phrase (Phrase Strings) : Provides powerful integration capabilities and APIs tailored to sync structured content fields with headless systems like Contentful, enabling automated pushes and pulls of translation jobs.
• GlobalLink (by TransPerfect) : A massive enterprise TMS featuring robust API connectivity (GlobalLink Now ) and pre-built connectors that handle automated submission, tracking, and re-injection of localized content for custom or headless tech stacks.
• TranslationOS (by Translated) : An AI-first localization platform that offers programmatic, real-time API integrations to shuttle content back and forth from headless CMS environments like Contentful with automated status tracking.

If you share which specific headless CMS you are currently using, I can tell you which of these TMS options has the most mature native connector for your exact setup.