This can happen if there’s a large amount of runtime packages being shipped to the client. There are some dependency management tools that can help, such as:
- https://packagephobia.com
- https://bundlephobia.com
- next.js/packages/next-bundle-analyzer at canary · vercel/next.js · GitHub
- https://bundlejs.com/
You can also use Vercel CLI to run a build locally and get more details