My profiler toolbar isn't showing up in symfony 4.3.1

It's very hard, if not impossible, to debug this for you remotely. The exact problem is tied to something specific in your local setup, and someone without access to your project would not have a chance to see exactly what is wrong.

Some general and specific troubleshooting advice for your situation:

1st. Reinstall the profiler pack

While unusual, the installation could be borked. Make sure your profiler package is alright.

First remove it (composer remove profiler), and then install it again: composer require --dev profiler).

2nd. Check the configuration

Use Symfony's console command to verify your configuration.

First for the built-in profiler:

$ bin/console debug:config framework profiler

Which should return something like this:

Current configuration for "framework.profiler"==============================================only_exceptions: falseenabled: truecollect: trueonly_master_requests: falsedsn: 'file:%kernel.cache_dir%/profiler'

And then for the profiler toolbar:

$ bin/console debug:config web_profiler

Which should return something like:

Current configuration for extension with alias "web_profiler"=============================================================web_profiler:    toolbar: true    intercept_redirects: false    excluded_ajax_paths: '^/((index|app(_[\w]+)?)\.php/)?_wdt'

3rd. Check the container

Check how the Profiler service will be instantiated:

$ bin/console debug:container profiler --show-arguments

Expect something like this:

Information for Service "profiler"================================== Profiler. ---------------- -------------------------------------------------------------------------------------  Option           Value ---------------- -------------------------------------------------------------------------------------  Service ID       profiler  Class            Symfony\Component\HttpKernel\Profiler\Profiler  Tags             monolog.logger (channel: profiler)                   kernel.reset (method: reset)  Calls            add, add, add, add, add, add, add, add, add, add, add, add, add, add, add, add, add  Public           yes  Synthetic        no  Lazy             no  Shared           yes  Abstract         no  Autowired        no  Autoconfigured   no  Arguments        Service(profiler.storage)                   Service(monolog.logger.profiler)                   1 ---------------- -------------------------------------------------------------------------------------

And then for the web_toolbar:

# bin/console debug:container web_profiler.debug_toolbar --show-arguments

For something like this:

Information for Service "web_profiler.debug_toolbar"==================================================== WebDebugToolbarListener injects the Web Debug Toolbar. ---------------- ------------------------------------------------------------------------  Option           Value ---------------- ------------------------------------------------------------------------  Service ID       web_profiler.debug_toolbar  Class            Symfony\Bundle\WebProfilerBundle\EventListener\WebDebugToolbarListener  Tags             kernel.event_subscriber                   container.hot_path  Public           no  Synthetic        no  Lazy             no  Shared           yes  Abstract         no  Autowired        no  Autoconfigured   no  Arguments        Service(twig)                   2                   Service(router.default)                   ^/((index|app(_[\w]+)?)\.php/)?_wdt                   Service(web_profiler.csp.handler) ---------------- ------------------------------------------------------------------------

(Note the 2, which enables the toolbar).

4th. Check the event dispatcher.

The web debug toolbar is injected during the kernel.response event. Check that the callback is appropriately hooked:

$ bin/console debug:event-dispatcher kernel.response

Which will return something like this:

Registered Listeners for "kernel.response" Event================================================ ------- -------------------------------------------------------------------------------------------- ----------  Order   Callable                                                                                     Priority ------- -------------------------------------------------------------------------------------------- ----------  #1      ApiPlatform\Core\Hydra\EventListener\AddLinkHeaderListener::onKernelResponse()               0  #2      Symfony\Component\HttpKernel\EventListener\ResponseListener::onKernelResponse()              0  #3      Symfony\Component\HttpKernel\DataCollector\RequestDataCollector::onKernelResponse()          0  #4      Symfony\Component\WebLink\EventListener\AddLinkHeaderListener::onKernelResponse()            0  #5      Symfony\Component\Security\Http\RememberMe\ResponseListener::onKernelResponse()              0  #6      ApiPlatform\Core\HttpCache\EventListener\AddHeadersListener::onKernelResponse()              -1  #7      Symfony\Component\HttpKernel\EventListener\ProfilerListener::onKernelResponse()              -100  #8      Symfony\Bundle\WebProfilerBundle\EventListener\WebDebugToolbarListener::onKernelResponse()   -128  #9      Symfony\Component\HttpKernel\EventListener\TestSessionListener::onKernelResponse()           -128  #10     Symfony\Component\HttpKernel\EventListener\DisallowRobotsIndexingListener::onResponse()      -255  #11     Symfony\Component\HttpKernel\EventListener\SessionListener::onKernelResponse()               -1000  #12     Symfony\Component\HttpKernel\EventListener\StreamedResponseListener::onKernelResponse()      -1024 ------- -------------------------------------------------------------------------------------------- ----------

Notice item #7, which is the Profiler collector (which among other things will include the X-Debug-Token header in the response, which will be later checked by the Web Debug Toolbar, which is item #8 in the above listing.

If any of the above checks fails

You'll have to focus on that specific part to find out why it is failing. Maybe some other bundle interfering? A problem with one of the configuration files?

Everything checks out

... but still not working? Well, that's weird. Make sure that your returned template has a </body> tag, and that the returned response has text/html content-type. But if all of the above checks out... it should work.

In a comment you say that framework.profiler.collect is set to false when performing these checks.

Set it to true by changing config/packages/dev/web_profiler.yaml like this:

framework:    profiler:        only_exceptions: false        collect: true

I had this problem too. I'm new to Sympfony, and I didn't knew, that .htaccess must be required via composer, if running on apache. Simply doing this:

composer require symfony/apache-pack

was the solution.

I had a similar symptom in a new Symfony 5.1 app - debug toolbar not displaying on some pages even though the project was in debug mode. Turned out in this app I had intended to have the <body></body> tags inside the twig template for each page, and not in the base template. But for a few pages (those that didn't display the debug toolbar), I had forgotten to include the <body></body> tags in the page template, so the rendered HTML had no <body> tag - hence debug toolbar will not display.