Dynamic routing is working on localhost but not on Vercel

[johnmehler-2660 (john)]

I have an API that loads test questions like this:
const response = await fetch(/api/study/questions/${testId}?limit=${settings.questions});

File location: src\routes\api\study\questions\[id]\+server.ts

On localhost, that API returns a response. On Vercel, it started returning a 404 less than a week ago.

It’s visible in the build logs:
.svelte-kit/output/server/entries/endpoints/api/study/questions/_id_/_server.ts.js

It’s visible in the resources tab for the build:
[/api/study/questions/[id]](/route/%2Fapi%2Fstudy%2Fquestions%2F%5Bid%5D?environment=all) IAD1 Node 22 2.66 MB

What’s happening is the dynamic routing is being interpreted literally:

1. https://cloudjobs.io/api/study/quiz/[id] - 200

2. https://cloudjobs.io/api/study/quiz/az305 - 404

First, was there a change that caused this? Because this was working fine until recently. Second, what changes do I need to make to get Vercel to recognize the dynamic routes?

[system]

There’s another community post with 404 debugging tips that might be helpful. Please give these solutions a try and let us know how it goes.

Debugging 404 Errors

Sometimes things don’t go as expected when deploying a website. If you see a 404 on your site, that means the page or resource couldn’t be found. There are many possible causes, and the absence of something can be tricky debug if you don’t know where to look. Here are some things you can do to find the cause and fix it. Debugging Tips Check the error code If you see a mostly white screen with 404: NOT_FOUND along with a Code and and ID then you can click the blue info box below the error deta…

A human should be around soon to offer more advice. But you can also get helpful information quickly by asking v0.

[johnmehler-2660 (john)]

I fixed this myself by changing from dynamic routing to URL parameters:

const id = event.params?.id; → const id = event.url.searchParams.get('id');

And changing the file path to not use the [id] directory.

[anshumanb (Anshuman Bhardwaj)]

I’m glad you found a fix. Thanks for sharing it with the community.