Features
Collections
Save requests into named collections for reuse. Collections appear in the sidebar and persist in IndexedDB.
- Save — Press Cmd+S to save the current request
- Organize — Drag and drop to reorder requests within a collection
- Context menu — Right-click a request to duplicate, rename, or delete it
- Load — Click any saved request to open it in a new tab
Environments & Variables
Define named sets of key-value variables and reference them anywhere with {{variableName}} syntax — in URLs, headers, body, params, and auth fields.
Creating Environments
Open the Environments panel in the sidebar. Create environments like “Development”, “Staging”, and “Production” with different base URLs, API keys, or tokens.
Switching
Only one environment is active at a time. Click the environment selector in the toolbar to switch. Variables resolve instantly.
Visual Indicators
- Variables that resolve successfully appear in amber
- Unresolved variables appear in red
Disabling Variables
Toggle individual variables on/off without deleting them — useful for temporary debugging.
Authentication
Rex supports 7 authentication methods, configured in the Auth tab:
| Method | Description |
|---|---|
| Bearer Token | Token in the Authorization header |
| Basic Auth | Base64-encoded username:password |
| API Key | Key sent as a header or query parameter |
| OAuth 2.0 | Authorization Code, Client Credentials, and PKCE grant types with automatic token refresh |
| AWS Signature V4 | Request signing for AWS services |
| Digest Auth | Challenge-response authentication with automatic retry |
| mTLS | Mutual TLS authentication |
OAuth 2.0 tokens are tracked with expiration times and refreshed automatically before they expire.
Body Editor
The Body tab supports multiple content types:
| Type | Use Case |
|---|---|
| JSON | API payloads with syntax highlighting and formatting |
| Form Data | Multipart form submissions with file uploads |
| URL-Encoded | Standard HTML form encoding |
| Raw | Plain text or any custom content type |
| GraphQL | Query editor with variables pane and introspection |
| None | No body (GET, HEAD requests) |
The editor uses Monaco (the VS Code editor engine) for syntax highlighting, formatting, and auto-complete.
Pre-Request & Test Scripts
Write JavaScript in the Scripts tab to run before sending (pre-request) or after receiving a response (test).
Pre-Request Scripts
Modify the request before it’s sent:
rex.request.headers.set("X-Request-ID", crypto.randomUUID());
rex.environment.set("timestamp", Date.now().toString());Test Scripts
Assert on the response and extract values:
rex.test("Status is 200", rex.response.status === 200);
const data = rex.response.json();
rex.test("Has user ID", data.id !== undefined);
rex.variables.set("userId", data.id);Available API
| Object | Scope | Methods |
|---|---|---|
rex.request | Pre-request | .url, .method, .headers.get/set, .body |
rex.response | Test only | .status, .json(), .headers |
rex.environment | Both | .get(key), .set(key, value) |
rex.variables | Both | .get(key), .set(key, value) |
rex.test | Test only | (name, assertion) — report pass/fail |
Scripts have a 5-second timeout. Logs, warnings, and errors are captured and displayed.
Request Chaining
Build sequences of dependent API requests in the Chains panel:
- Create a chain and add steps (each step references a saved request)
- Configure variable overrides per step
- Add pre-request and test scripts to extract values
- Set failure handling: stop, skip, or retry (with configurable attempts)
- Run the chain and watch real-time progress with pass/fail indicators
Chains are useful for workflows like: authenticate → create resource → verify creation → clean up.
WebSocket
Connect to WebSocket endpoints (ws:// and wss://) from the request builder:
- Send and receive messages in real-time
- View a timestamped message log with direction badges (sent/received)
- Support for subprotocols
- Binary message handling
- Connection state indicators (connecting, connected, error)
Server-Sent Events
Connect to SSE endpoints to watch events arrive in real-time:
- Event type and payload display
- Timestamps on each event
- Auto-scroll with manual override
- Expandable event details
GraphQL
Switch the body type to GraphQL for a dedicated editing experience:
- Query editor with syntax highlighting
- Variables pane (JSON format)
- Operation name selector
- Schema introspection — Rex fetches the schema from the endpoint and provides autocomplete for types, fields, queries, mutations, and fragments
Response Viewer
Responses are rendered based on content type:
| Content Type | Rendering |
|---|---|
| JSON | Syntax highlighted with line numbers and auto-formatting |
| HTML | Inline iframe preview + raw source view |
| Images | Inline display with dimensions |
| Built-in PDF viewer | |
| XML | Auto-formatted with indentation |
| Binary | Hex dump with download option |
Status codes are color-coded: green (2xx), blue (3xx), amber (4xx), red (5xx).
History & Diff
Every request is automatically logged in the History panel with the full request and response.
- Search by URL, method, or status code
- Filter by time range
- Diff — Select any two history entries to compare body, headers, and status side by side with line-by-line change highlighting
DevTools Integration
Rex appears as a panel in Chrome DevTools (F12):
- Open DevTools on any page
- Switch to the Rex tab
- Browse the page — captured network requests appear in the panel
- Click Send to Rex to load a request into the main app
- Or select multiple requests and Import as Collection
Filter captured requests by type (XHR/Fetch only or all) and search by URL.