Add the 'Initiator' column to the Network Panel if it's not there already. It will show you how a resource was initiated. Examples include:

• Parser - Maybe a regular <script> tag in the HTML document
• Redirect - A HTTP redirect caused the resource to initate
• Script - Some JavaScript (e.g. new Image()) initiated the resource
• Other - It was another process.

Update - New in DevTools: (tweet) this will now work for images loaded asynchronously. You now get the full JavaScript stack trace.

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