.htaccess tester

Paste your .htaccess and a URL. You get every RewriteCond with the value it was actually tested against, every RewriteRule that matched or didn’t, and what Apache would finally do with the request.

This runs entirely in your browser. Your .htaccess is not uploaded, not logged, and not sent anywhere — there is no server behind this page, only a static file and the simulator compiled to JavaScript. No account, no email address, no limit on how many times you use it.

Why your rule didn’t fire

Four causes account for most of it, and the trace above names which one you have:

An earlier rule already matched and carried [L]. Processing of that pass stopped there. The trace shows the rule that won.
A RewriteCond failed. Conditions are tested against an expanded string, not the one you wrote; the trace prints the expanded value next to the pattern.
The pattern is matched against a path with no leading slash. In a per-directory .htaccess, Apache strips the directory prefix before matching, so ^/blog never matches anything.
The rewrite loops. If a pass changes the path, the whole file runs again. Ten passes later Apache gives up and returns 500. The third example above is that.

Limits, stated plainly

File tests are assumed false. RewriteCond %{REQUEST_FILENAME} !-f cannot be answered without your filesystem, so the simulator assumes the file does not exist and says so on the line. That is the common case for a front controller and the wrong case if you are debugging a rule that depends on a file existing.
Patterns use your browser’s regular-expression engine, not Apache’s PCRE. They agree on ordinary rewrite patterns and disagree at the edges; where a ruleset uses a construct the browser cannot compile, the page says so above the trace instead of guessing.
Per-directory rules only. RewriteBase, RewriteMap, proxying and server-config context are not modelled.
Some rule flags are recognised and reported but not simulated. They are listed in the output when your file uses one.

The same engine, inside your IDE

This page is the parser, simulator and validator from .htaccess Pro, a JetBrains IDE plugin, compiled to JavaScript. Same code, no second implementation. In the IDE it runs against the file open in your editor, and double-clicking a line of the trace jumps to that line of the file.

The plugin is free while in early access. Add https://theseusbuilds.pages.dev/htaccess-pro/updatePlugins.xml under Settings → Plugins → gear → Manage Plugin Repositories, then install “.htaccess Pro”. Current version 1.0.3.

The engine is also open source under the MIT licence, as a command-line tool: github.com/theseusbuilds/htaccess-trace — npx github:theseusbuilds/htaccess-trace .htaccess /blog/hello-world.

Found a file this gets wrong? That is the most useful thing you can send me: hello@theseusbuilds.dev.