Clarify that `X-GitHub-Delivery` is unique per event, not per delivery

[minusworld]

Code of Conduct

• [X] I have read and agree to the GitHub Docs project's Code of Conduct

What article on docs.github.com is affected?

https://docs.github.com/en/webhooks/webhook-events-and-payloads#delivery-headers https://docs.github.com/en/webhooks/using-webhooks/best-practices-for-using-webhooks#use-the-x-github-delivery-header

What part(s) of the article would you like to see updated?

https://docs.github.com/en/webhooks/webhook-events-and-payloads#delivery-headers https://docs.github.com/en/webhooks/using-webhooks/best-practices-for-using-webhooks#use-the-x-github-delivery-header

Additional information

Hi there!

I was experiencing a puzzling issue for a while where were receiving two webhook event payloads with the same X-GitHub-Delivery GUID. At first, I assumed it was our infrastructure duplicating something because I assumed that all payloads from GitHub would have a unique X-GitHub-Delivery. However, upon further experimentation, I was able to create a scenario which sends two different payloads with the same X-GitHub-Delivery GUID by creating two GitHub Apps. This leads me to believe that X-GitHub-Delivery is unique per GitHub event, not unique per delivery as the documentation implies. Further, this means the guidance in this section is nuanced because there are cases where I want to handle the webhook differently based on which App is sending the event, which means excluding payloads based on X-GitHub-Delivery isn't always valid.

Below are some screenshots showing the same X-GitHub-Delivery from two different GitHub Apps.

1. I created two GitHub Apps to send webhook events to two different callback URLs.

2. This screenshot shows the same X-GitHub-Delivery GUID routed to two destinations.

Additionally, it shows unique Amazon CloudFront and Amazon Load Balancer IDs for the web request.

3. This screenshot shows the same X-GitHub-Delivery with two different app_ids.

[welcome[bot]]

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[nguyenalex836]

@minusworld Thank you for opening this issue! I'll get this triaged for review ✨

[github-actions[bot]]

Thanks for opening an issue! We've triaged this issue for technical review by a subject matter expert :eyes:

[tiabas]

The X-GitHub-Delivery header is indeed only unique per Event and not per delivery. Is a repository had 10 apps listening to the same event, all these apps would receive the same delivery payload for that event.

cc: @skedwards88

[skedwards88]

Thanks for the confirmation, Kevin, and thanks for this detailed and clear issue @minusworld !

You or anyone else is welcome to open a PR to clarify this:

• Update the description of X-GitHub-Delivery in https://docs.github.com/webhooks/webhook-events-and-payloads to clarify that this ID is unique per event (not per delivery)
• Update the "Use the X-GitHub-Delivery header" section in the best practices article to clarify that this ID is unique per event (not per delivery)

[dxkf177]

Code of Conduct

• [x] I have read and agree to the GitHub Docs project's Code of Conduct

What article on docs.github.com is affected?

https://docs.github.com/en/webhooks/webhook-events-and-payloads#delivery-headers https://docs.github.com/en/webhooks/using-webhooks/best-practices-for-using-webhooks#use-the-x-github-delivery-header

What part(s) of the article would you like to see updated?

https://docs.github.com/en/webhooks/webhook-events-and-payloads#delivery-headers https://docs.github.com/en/webhooks/using-webhooks/best-practices-for-using-webhooks#use-the-x-github-delivery-header

Additional information

Hi there!

I was experiencing a puzzling issue for a while where were receiving two webhook event payloads with the same X-GitHub-Delivery GUID. At first, I assumed it was our infrastructure duplicating something because I assumed that all payloads from GitHub would have a unique X-GitHub-Delivery. However, upon further experimentation, I was able to create a scenario which sends two different payloads with the same X-GitHub-Delivery GUID by creating two GitHub Apps. This leads me to believe that X-GitHub-Delivery is unique per GitHub event, not unique per delivery as the documentation implies. Further, this means the guidance in this section is nuanced because there are cases where I want to handle the webhook differently based on which App is sending the event, which means excluding payloads based on X-GitHub-Delivery isn't always valid.

Below are some screenshots showing the same X-GitHub-Delivery from two different GitHub Apps.

1. I created two GitHub Apps to send webhook events to two different callback URLs.

### 2. This screenshot shows the same `X-GitHub-Delivery` GUID routed to two destinations. Additionally, it shows unique Amazon CloudFront and Amazon Load Balancer IDs for the web request.

3. This screenshot shows the same X-GitHub-Delivery with two different app_ids.

[dxkf177]

See

[CBID2]

Hi @nguyenalex836. I made a pull request for this issue. It's #33184.