This post assumes that you've built and deployed your application to render or digitalocean but your website gives the 404 error like the one below after refreshing or clicking on a link.

For render, go to Redirects/Rewrites and do the following:

• Under source, add /*

• Fill /index.html as destination

• For action, choose "rewrite"

For digital ocean:

• Navigate to your App -> Components -> Select the static site -> Expand the “Custom Pages” section. There, choose “Catchall” for the type and enter index.html as the page name.

This works for SPAs using react-router for navigation. Should work for some others as well.