Make very large payloads visible in VCL using custom headers

Using the Fetch API in JavaScript, it's possible to add custom headers to a request and see that data in VCL, which is subject to a much higher limit than those that we place on URL length and exposed POST body.

VCL

Use this solution in your VCL service (click RUN below to test this solution or clone it to make changes):

User contributed notes

We welcome comments that add use cases, ideas, tips, and caveats. All comments will be moderated before publication. To post support questions, visit our support center and we'll find you the help you need.