Requestly has two halves. Its API client is the same job as Postman's, and an agent builds a local one in a sitting. The half people know it for is the browser interceptor that redirects URLs, rewrites headers, injects scripts and fakes API responses. A Chromium extension covers most of that with declarativeNetRequest rules, but changing response bodies needs a page-level script that patches fetch and XMLHttpRequest, and Firefox, Safari or a phone's traffic need more work again. The weekend goes on those edges and on keeping rules working as sites change.
Before you buildRequestly shows no free plan now, only a 30-day trial. Header Editor, Mockoon and mitmproxy are free and cover simple redirects, header changes and mocks without building anything.
Build me a browser request-rewriting extension to replace Requestly. Requirements: - A Chrome Manifest V3 extension in TypeScript, built with Vite and `@crxjs/vite-plugin`. `npm run build` writes ./dist, which loads unpacked; Vitest for the rule logic. - Rules live in chrome.storage.local as JSON: id, name, enabled, a URL condition (contains, wildcard or regex, plus optional methods and resource types) and one action. - Actions done with `declarativeNetRequest` dynamic rules: redirect to a URL, block, set, append or remove request and response headers, change query parameters, replace the host. Warn in the UI when the dynamic rule limit is close. - Mock response: a content script in the MAIN world at document_start patches fetch and XMLHttpRequest and returns the configured status, headers, JSON or text body after an optional delay. The UI must say it cannot touch service-worker or other extensions' requests. - Script rules: inject a JavaScript or CSS snippet into matching pages with `chrome.scripting`. - Options page in React: rules with enable switches, drag to reorder, groups switched on together and a "test this URL" box. A popup lists the rules that matched on the active tab, using `declarativeNetRequest.onRuleMatchedDebug` (unpacked extensions only; say so). - Import and export all rules as one JSON file with a schema version number. - No accounts, no telemetry, local-first: the extension makes no network calls of its own and requests only the permissions it uses. - Out of scope: Firefox and Safari, traffic from other apps or phones, team sync, an API client. - README: loading the unpacked build, which actions work where, and the limits of Manifest V3.
Opens your agent with the prompt filled in, you press enter. Or copy it and paste it into an empty folder.
The first prompt builds the core. Run these one at a time in the same folder to grow it into your own Requestly.
Add a traffic recorder to the extension in this folder. Requirements: - A "Record" toggle in the popup that logs method, URL, status and resource type of requests in the active tab using `chrome.webRequest` observers (no blocking), kept in memory only. - A list in the options page with a filter box; each row has "Mock this" and "Redirect this" buttons that open a prefilled rule with the exact URL as the condition. - For "Mock this", re-fetch the response body once and prefill it, with a size limit of 200 KB. - Recording stops when the tab closes. Update the README.
Add read-only rule groups loaded from a URL to the extension in this folder. Requirements: - In the options page, add a group by pasting a raw JSON URL; fetch it, validate it against the rule schema and show a diff against the cached copy before applying. - Re-check on demand with an "Update" button and, if enabled, once a day with chrome.alarms. - Remote groups cannot add script or CSS injection rules unless the user ticks a per-group box. - Show the source URL and last update time. Update the README.
Add network-condition rules to the extension in this folder. Requirements: - A new action that delays matching fetch and XMLHttpRequest calls by a fixed or random range in ms. - A new action that fails a share of matching requests (0-100%) with a chosen status code or a network error, deciding per request at random. - Show a small badge on the toolbar icon while any of these rules is enabled. - Add tests for the random-range and percentage logic. Update the README.
Front-end and QA engineers use it to try a fix or a broken API response without touching the backend, and the paid plans let a team share the same rules and API collections. One vendor keeps the extension working across browsers while sites and browser rules keep changing.
Estimate · A local extension with nothing to host. The build is token usage on your agent plan; expect a second session for site-specific edge cases.
| Plan | Monthly | Annual, per month | What you get |
|---|---|---|---|
| Team | $12/user | $10/user | API client for REST, GraphQL, SOAP, gRPC, WebSocket and MQTT; Local Projects with two-way GitHub and GitLab sync; Team Projects with real-time collaboration; unlimited manual and scheduled collection runs; basic API design and docs; imports from Postman, Insomnia and Bruno. |
| Team Pro | $18/user | $15/user | Everything in Team plus unlimited AI credits, AI test and assertion generation, AI debugging, advanced test reporting, a secret scanner and vault integrations (HashiCorp, Azure Key Vault, 1Password). |
| Enterprise | custom | — | Add-on to Team or Team Pro: SSO and SCIM, attribute-based access control, audit logs with SIEM export, data residency or self-hosting, priority support. |
The pricing page lists no permanent free plan, only a 30-day trial with full Team Pro features and no card.
Kinda. The core is a weekend build with the prompt on this page, but real gaps remain: Extensions for Firefox and Safari, and the desktop apps for macOS, Windows and Linux, Team Projects with real-time collaboration and shared rule sets.
About $12 a month on the Team plan per seat, $144 a year (checked 2026-10-19).
Extensions for Firefox and Safari, and the desktop apps for macOS, Windows and Linux; Team Projects with real-time collaboration and shared rule sets; The API client's collection runs, scheduled cloud runs and AI test generation; Two-way Git sync and one-click imports from Postman, Insomnia and Bruno. If any of those matter to you, keep paying.
Yes: Header Editor (open source), mitmproxy (open source), Mockoon (open source).