# Profiling HTTP Requests with a Browser

Using a browser is the easiest way to profile **web applications**.

To get started, check that you have Blackfire [installed](../up-and-running/installation) correctly on the server hosting the website you want to profile and install the [Firefox](../integrations/browsers/firefox)extension or the [Google Chrome](../integrations/browsers/chrome) one.

> **Tip**
>
> If you need more flexibility, like profiling APIs, `POST` requests, or adding specific HTTP headers, use the [Blackfire CLI](profiling-http-via-cli) instead.

## Profiling

To profile a web application from Firefox or Google Chrome:

- Log in on [Blackfire.io](https://blackfire.io/login);

     ![](../images/companion-unauth.png)
- Browse to the URL you want to profile;
- Open the extension by clicking on its icon in the browser toolbar;

     ![](../images/companion-auth.png)
- Click on the "Profile" button;
- After a few seconds, click on "View Call Graph" or "View Timeline".

     ![](../images/companion-toolbar.png)

## Copy-As-cURL in your Browser

Did you know that browsers can give you the cURL arguments and options like HTTP headers to use for any web page you browse? Including Ajax requests?

This feature is known as "copy-as-cUrl". The result can be used directly with the [Blackfire CLI](profiling-http-via-cli) to profile requests from the command line and to automate profiling in scripts:

![](../images/chrome-copy-as-curl.png)

![](../images/firefox-copy-as-curl.png)

## Profiling all Requests

If you want to profile all pages from a session, open the extension and click on the "[Profile all requests](profiling-http-via-browser#profiling-all-requests)" link, then click on the *Record!* button.

Blackfire will then profile all requests including POST requests, Ajax requests, and API calls.

A pop-over window will open at the bottom right of your browser window, where all profiled requests will be listed. Stop the session by clicking on the *Stop* button.

All profiled requests will be available on your [dashboard](https://blackfire.io).

> **Warning**
>
> The "[Profile all requests](profiling-http-via-browser#profiling-all-requests)" feature is currently unavailable on Chrome due this [browser limitations](../integrations/browsers/chrome#profiling-all-requests-chrome).

## Limitations on 304 HTTP Responses

The browser extensions are not able to profile 304 HTTP responses as some Web Servers remove custom headers such as the ones added by Blackfire to operate correctly. To avoid 304 HTTP responses, the browser extensions remove any conditional headers from requests; if you want to profile 304 responses, use the Blackfire CLI `curl` command instead.