Hi, @quick007! Welcome to the Vercel Community 😄

We wrote a community post about how to debug these errors, could you have a look and let us know how you get on? https://community.vercel.com/t/debugging-404-errors/437

Hi pawlean!

I tried my best to follow those steps, but the vercel build command doesn't work locally because I have a windows machine (likely also why it works locally with my pnpm build and start commands, but not on vercel). Please note that my project is properly deployed, it's just that some pages are returning 404s that work fine locally.

When looking at the output in the source tab, I can see that the pages are there, but they have the code for slashes instead of a proper / and when I try to click on the file, I get a weird error (see screenshots below).

Output file structure:

Error when I try to click on one:

Thanks for sharing the repo! That was very helpful. 🙂

It looks like a problem with the MDX configuration. I made a few changes based on the Next.js MDX configuration doc to get it working in a preview deployment:

• install @next/mdx (other needed packages were already installed)
• modify next.config.mjs

  1import createMDX from '@next/mdx'2 3/** @type {import('next').NextConfig} */4const nextConfig = {5  // Configure `pageExtensions` to include markdown and MDX files6  pageExtensions: ['js', 'jsx', 'md', 'mdx', 'ts', 'tsx'],7  // Optionally, add any other Next.js config below8}9 10const withMDX = createMDX({11  // Add markdown plugins here, as desired12})13 14// Merge MDX config with Next.js config15export default withMDX(nextConfig)

You can find the full details here:

https://nextjs.org/docs/app/building-your-application/configuring/mdx

Hi Amy,

I'm loosely basing my repo on the example that vercel made. That example uses the package next-mdx-remote, which seems to be a more comprehensive MDX solution for blogs and works better for the way that I want to structure my content.

I did try using the @next/mdx package, but it would require me to refactor a decent amount of my code and overall isn't a super ideal solution.

Again, my blog works without error locally, but doesn't work on vercel.

Thanks for sharing that additional context. The dev command doesn't work exactly the same as a deployment. It may work locally because the files are still present on your local computer even if they're not included in a build. It still appears to be a configuration difference as the example project does work as expected.

It looks like there is quite a bit different between your example and that starter project. I recommend reviewing the things you changed from that starter project to identify which difference is causing the odd build output.