Open Headers

The open-source Enterprise API client in your browser. Team
Collaboration. Browser Interceptor - modify live traffic.

Local-first: no account, no cloud, your data stays on your machine.

Website: openheaders.com ·
Docs: docs.openheaders.com
Community: Discord ·
r/openheaders ·
Discussions

What it does

API Client — manage and execute requests

• Requests: HTTP, GraphQL, gRPC, MQTT, WebSocket, Socket.IO, SSE
• Structure: Collections > Folders > Requests
• Scripting: pre- and post-response scripts and assertions, with a
  package library
• Settings: execution and limits, connection, TLS and trust,
  redirects, cookies, session, session resilience
• Authorization: inherited through the structure, overridable per
  request: API Key, Basic Auth, Bearer Token, Digest Auth, Hawk, HTTP
  Message Signature, JWT Bearer, OAuth 1.0, OAuth 2.0, AWS Signature v4,
  Akamai EdgeGrid, ASAP (Atlassian)
• Specs: OpenAPI 3.1 (HTTP), Protobuf 3 (gRPC), AsyncAPI 3.0
  (WebSocket, MQTT), GraphQL schema (GraphQL)
• Delegation: send from the browser extension, or run/delegate the
  request on the desktop app or the server
• Workflows: schedule multiple linked requests with AND/OR
  conditions and auto-refresh, then extract live variable values from
  the responses
• Variables: Workspace (global), Collection, Environment, Vault
  (secret), Live

Browser Interceptor — modify live browser traffic

• Rules: API HTTP request and response, headers, query params,
  JS/CSS, WebSocket, SSE, block, redirect, delay, auth challenge
• Structure: Collections > Folders > Rules
• Modify API HTTP responses: mock, or rewrite the server's; body as
  static data or dynamic JavaScript; optionally modify headers and
  override the status code
• Modify API HTTP requests: REST or GraphQL; body as static data or
  dynamic JavaScript
• Modify WebSocket messages and SSE events
• Modify headers, query params and URLs
• Inject JS and CSS
• Block and redirect requests
• Respond to auth challenges
• Variables: every rule reads the same variable scopes; Live
  variables filled by API Client workflows make prod-like scenarios
  possible
• DevTools panel: a custom Open Headers panel in the browser's
  DevTools, with enterprise design and features

Team Collaboration — manage shared workspaces

• Multi-workspace: your personal workspaces and the team's shared
  workspaces, side by side
• Backup and sync: through a local server you self-host or a remote
  server you join
• Server features: SSO, RBAC user management, audit logs
• Git integration: durable workspace history, embedded version
  control tools
• Concurrent multi-user editing: CRDT-flavoured writes for the
  workspace data
• Work offline: auto-sync when back online

Enterprise Platform — free, like it should be

• Tools: every major feature is embedded in its own Tool panel
• Modern UI: minimalist workbench canvas with two active sidebars
  and six dock regions
• Modern UX: drag and drop the Tools across the dock regions to
  group them
• One user interface: desktop app, web app and browser extension
  (workbench and browser DevTools panel)
• Embedded documentation: info popovers and a Docs Tool with
  diagrams and text, usable offline
• Git: version control and commit changes directly inside the
  desktop app
• Traffic: route the browser traffic to the desktop app and modify
  it there
• AI integration: use your existing subscriptions with the MCP
  server and automate interaction with your workspace data and Tools

Get started

Install the extension:

• Chrome Web Store
• Edge Add-ons
• Firefox Add-ons

Install the desktop app:

• macOS
• Windows
• Linux

Self-host your own server:

• macOS
• Linux
• Docker

To build any app from a fresh clone, see
Building each app in the
developer guide.

Security & trust

• Security policy — how to report vulnerabilities, safe
  harbor for good-faith research
• Security whitepaper — the architecture
  behind the guarantees
• Wire transparency — every outbound call,
  byte for byte
• Privacy policy — data practices
• Extension permissions — why each
  browser permission is requested

Documentation

• docs.openheaders.com — quick starts,
  guides, the server book, command reference
• Architecture overview — the system map
• Developer guide — setup, builds, tests, CI
• Contributing — bug reports, DCO sign-off,
  feature policy

License

Open Headers is open source under the Apache License 2.0.
Official branded binaries and store builds are distributed under the
End User License Agreement. Every feature is included
in the free tier — the software is identical on every plan, and paid
plans exist only to add team seats beyond the free tier's six active
users.