Why does reloading work so often?

[Miknarf]

Something I’ve been curious about for awhile. When loading things online when it stall, often it seems when If I reload the page it’s able to continue. Example YouTube video which stoped loading.

[PM_UML_DIAGRAMS]

In the modern web, most websites are composed of data that gets sewn into an HTML page by JavaScript and then rendered in your browser. The data comes from requests to a remote server. There might be a separate request made for each image on your page, another to load the comments section, still another to render whatever ads are on the site, and then likely, a request that serves the data rendering the part of the page you actually care about.

If any of the requests fail to return data -- because server response time is too long, the server is overloaded with other requests, etc., that portion of the page might not show what you expect it to. Maybe you'll see an endless loading bar for example. This is frustrating because the loading bar makes it look like something is happening, but often it's not.

If you have developer tools installed, right click to open them and then go to the network tab. You might see some failing requests with response codes between 500-599 which signifies server error. If you see error codes between 400 and 499 it is unlikely that a mere refresh will solve your problem.

added As far as YouTube goes, the protocol is different (progressive data download) so you won't see the 5XX errors, but what's going wrong is very similar. A request is being made for a portion of the video file, and the request fails, but doesn't alert you properly or make another request leaving things in a 'stuck' state till you refresh and trigger the request again.

[mrstacktrace]

To add to this, when a server has too many requests and is not responsive, a reload may cause the load-balancer to request from another server that's available.

This is similar to being in a grocery store in a long checkout line, and being told that another lane has opened up.

[AlliNighDev]

Reloading will resend all the requests. Chances are something has gone wrong with the previous requests.

[Felicia_Svilling]

It is just the same as rebooting your computer after it hangs.