Importing from Safari

To record a performance profile in Safari, open the developer tools and switch to the "Timelines" tab.

Click the red record button in the top left to start a profile.

When you're done recording, click the stop button in the top left to end the recording.

To export the resulting profile, click the "Export" button in the top right.

This should export a file like www.my-website.com-recording.json

You should be able to open that file in https://www.speedscope.app/.

To view it offline, you'll need to install speedscope via npm:

npm install -g speedscope

Then you should be able to open it like so:

speedscope /path/to/profile.json