ReqFlex

ReqFlex is a developer extension that lets you freely add, modify, and remove HTTP request and response headers. It's useful whenever you need to temporarily rewrite headers to test behavior — during API development, general testing, or authentication-related work. ■ Useful for situations like - Testing API endpoints with authentication tokens or Basic Auth credentials you can't configure directly - Adding temporary development-only custom headers that production servers won't accept - Rewriting response headers (cache settings, CORS permissions, etc.) to verify how the browser reacts - Applying headers to specific sites only, without affecting anything else - Switching between different header configurations for different environments (development, staging, production) ■ Key features - Profiles: create multiple named configurations for different purposes, and toggle each one independently. Multiple profiles can be active at the same time - Add, modify, or remove request headers: attach new headers, rewrite existing values, or strip specific headers from outgoing requests - Add, modify, or remove response headers: edit headers coming back from the server the same way - Quick setup for common headers: generate a Basic Auth header just by entering a username and password, or a Bearer token header by entering the token - URL filters: apply a profile only to requests matching a specific URL pattern, so unrelated sites are never affected - Use current tab's URL: fill the URL filter field with the active tab's address in one click - Import/export: save your profiles as a JSON file and load them on another machine or environment - Input validation: invalid characters in header names or values are flagged immediately - Localized into 10 languages: English, Japanese, Korean, Chinese (Simplified & Traditional), Thai, Vietnamese, French, Italian, and German, automatically matching your browser's language (or chosen manually in settings) ■ Why install it - No data ever leaves your browser — all settings are stored locally and nothing is sent to an external server - Built on Manifest V3's declarativeNetRequest API, so it works with the latest Chrome extension architecture - Free to use - A simple interface that's easy to configure even on first use ReqFlex is built to make development and testing work faster. Give it a try.