htmx-debugger is a powerful browser extension (compatible with Chrome and Firefox) designed to help developers debug and analyze htmx applications. It provides a comprehensive and user-friendly interface for viewing htmx events, requests, and responses in real-time. This tool is essential for understanding and troubleshooting htmx-powered web applications, making the development process smoother and more efficient.
- Real-time capture and display of htmx events
- Support for htmx 2 and htmx 4.0.1 event names
- Events grouped by target element, with repeats of the same event folded into one entry
- A timestamp for every occurrence of each event
- Fetch response status and headers for htmx 4 events, and XHR details for htmx 2 events
- Events fired before the DevTools panel opens are kept (up to 250 per tab) and shown when it opens
- Search to filter events by their content
- One-click clear button to reset the debugger view
- Event filtering (All, Requests, Responses)
- Collapsible event details for a cleaner interface
- Live connection status indicator
- Automatic periodic connection checks for improved stability
- Error handling that pauses capture after repeated failures instead of flooding the console
- Export functionality to save captured events as a JSON file
- Import capability to load and analyze events from a JSON file
- Visit the htmx-debugger page on the Chrome Web Store.
- Click the "Add to Chrome" button.
- Confirm the installation when prompted.
- Clone this repository or download the source code.
- Open Google Chrome and navigate to
chrome://extensions/. - Enable "Developer mode" by toggling the switch in the top right corner.
- Click on "Load unpacked" and select the directory containing the extension files.
- The htmx-debugger extension should now appear in your list of installed extensions.
- Visit the htmx-debugger page on the Firefox Add-Ons website.
- Click the "Add to Firefox" button.
- Confirm the installation when prompted.
- Download the latest release file for Firefox browsers.
- Open Firefox and navigate to
about:debugging#/runtime/this-firefox. - Click on "Load Temporary Add-on..." and select the downloaded release file.
- The htmx-debugger extension should now appear in your list of installed extensions.
- Navigate to a webpage that uses htmx.
- Open DevTools (Right-click > Inspect or press F12).
- Look for the "htmx" tab in the DevTools panel. If you don't see it, click on the ">>" icon to find it in the list of additional tools.
The debugger automatically captures htmx events as they occur on the page. Each event is displayed with the following information:
- Event type
- Timestamp
- Target element details
- Event-specific details
- Fetch response status and headers for htmx 4 events, or XHR details for htmx 2 events
- Connection Status: Check the connection status indicator in the panel header to ensure the debugger is properly connected.
- Search: Use the search bar at the top to filter events based on their content.
- Clear: Click the "Clear Events" button to reset the debugger and remove all captured events.
- Event Filtering: Use the All, Requests and Responses buttons to show all events, only request events, or only response events.
- Expand/Collapse: Click on a group or event header to expand or collapse its details.
- Repeated Events: When the same event fires again on the same element, its timestamp is added to the existing entry instead of a new entry.
- If you don't see any events in the debugger, ensure that the webpage you're debugging is actually using htmx.
- If the htmx tab doesn't appear in DevTools, try reloading the page or reopening DevTools.
- Check the browser console for any error messages related to the extension.
- If the connection status shows "Disconnected", try reloading the page. If it stays disconnected, close and reopen DevTools.
- If problems persist, try disabling and re-enabling the extension, reloading the webpage, or restarting the browser.
background.js: Background script (a service worker in Chrome) that relays events from content scripts to the panel and holds them until the panel openscontent.js: Content script for capturing htmx events and communication with background scriptdevtools.html: DevTools page that loadsdevtools.jsdevtools.js: Registers the "htmx" DevTools panelmanifest.json: Chrome extension manifest (Manifest V3), including permissionsmanifest-firefox.json: Firefox extension manifest (Manifest V2), used for the Firefox buildpanel.html: Panel HTML for displaying captured events and debugger controlspanel.js: Panel functionality for handling event display and debugger features
There are many other build/development-related files in addition to those listed above. If you're contributing or modifying for your own purposes you should recognize these. bun run build (PowerShell 7) lints, builds the CSS, formats, and writes the Chrome and Firefox zips to releases/.
htmx-debugger is committed to protecting user privacy and does not collect or use any personal user data. The extension operates solely within the context of the user's browser to provide debugging functionality for htmx applications.
The Chrome build requests one API permission. The Firefox build (Manifest V2) also declares activeTab.
- alarms: The alarms permission schedules the background script's periodic housekeeping: a keep-alive ping every minute, an hourly reset of its message counter, and a log of its message count and queue size every five minutes. The connection checks between the page, the background script and the panel use ordinary timers.
The single purpose of htmx-debugger is to provide a comprehensive debugging tool for web developers working with htmx-powered applications. It captures, displays, and analyzes htmx events in real-time, offering insights into the behavior of htmx interactions within web pages.
htmx-debugger complies with both the Chrome Web Store Developer Program Policies and the Firefox Add-Ons policies regarding data usage. The extension:
- Does not collect any personal user data
- Does not transmit any captured debugging information outside of the user's browser
- Only processes information necessary for its core debugging functionality
- Does not store captured events: they are held only in the extension's memory (in the background script until the DevTools panel opens, then in the panel) and are never written to storage
By using htmx-debugger, users can be assured that their privacy is respected and that the extension operates within the bounds of its stated purpose as a development tool for htmx applications.
- v1.2.2 (2026-11-04): Captured the released htmx 4.0.1 final-swap event and Fetch response details, improved response filtering and panel reconnection, and made the release build stop on failed steps
- v1.2.1 (2026-07-30): Fixed the console flood on pages that boost forms, quieted the content script's per-page logging, and removed the htmx.process wrapper that never ran
- v1.2.0 (2026-07-30): Added htmx 4 event support, replayed events captured before the DevTools panel opens, and cleaned up extension reload and rate-limit errors
- v1.1.1 (2026-07-29): Fixed the Tailwind v4 distribution build and aligned the browser manifest versions
- v1.1.0 (2026-07-29): Added parsed HTTP response headers to XHR event logging, added xhr:abort event capture, migrated build toolchain from npm to bun
- v1.0.6 (2024-10-22): Added HX attributes to target element details, added snapshot information, added error handling and reporting, further reduced console log output
- v1.0.5 (2024-10-11): Before/after request/response event capture, removed activeTab permission, reduced console log output
- v1.0.4 (2024-10-03): Fixed excessive permissions per Google review
- v1.0.3 (2024-10-02): Minor update and new Firefox release, fixed sanitization issue recommended by Firefox
- v1.0.0 (2024-09-30): Initial release, core features implemented, Chrome Web Store release
For a detailed changelog, see CHANGELOG.md.
This project is licensed under the MIT License. See the LICENSE file for details.
For any questions, support, or feedback, please contact the author through standard channels.
The source code for this project is available on GitHub:
https://github.com/NomadicDaddy/htmx-debugger
For bug reports or feature requests, please use the issue tracker.