Firefox for Android showing "There is a more recent version of the page [...], do you want to reload?"

Question

When I reopened Firefox after a few hours, it normally opens the last website I've viewed, but it displayed for a second a strange message popup similar to:

There is a more recent version of the page on the server, do you want to reload?

(maybe it's not the exact phrase because of my translation and that I may have not read the popup correctly).

I opened Firefox about 4 hours before, then left Firefox on standby on the phone. Then I reopened the site without refreshing when I saw the notification above.

I have no malware on the smartphone, and it was just a normal website about cars.

What does the notification mean?

Answer 1

The message "there is a more recent version of the page on the server, do you want to reload?" is shown by the website itself. It is generated via JavaScript and other web techniques and therefore can vary by size, displayed text, and other properties.

When you re-open Firefox, the previously cached web page is displayed. Some websites use special web techniques (JavaScript + WebSocket) to connect to the server in the background and check for provided update information.

For example, the Stack Overflow/Stack Exchange web pages also use this technique for displaying an info header that new questions are available or that there is a new message in your "inbox".

Therefore, if your browser first loads the cached page and then checks for updates and displays this message. As the message is generated by the web page, not by the web browser itself, it will only appear on web pages that use this technique and it may look totally different on each page.