Parameter on tag

Question

I found that some website use parameters on image src like ?v=1390510765392

what is it used for ?

<img src="image.jpg?v=1390510765392" />

Found on that Angularjs example

Duplicate http://stackoverflow.com/questions/11397942/why-querystrings-after-images-css-files — steveax, Jan 23 '14 at 21:18

score 2 · Accepted Answer · answered Jan 23 '14 at 21:10

I can think of two possible uses...

If the parameter randomly changes every time the page is loaded, then it's a common means of preventing the browser from caching the image. This would force the browser to always request a new one (because the URL is different) so that the user always has the latest version.
If image.jpg isn't actually an image but rather a code-driven server-side resource which responds with an image, then URL parameters would be a way to pass an identifier to that resource to identify which specific image data to download. (Such as if the images, or at least references to them, are stored in a database.)

The first one is very likely what's happening here, though the second is certainly possible.

I use technique #1 with CSS background images which are generally cached more aggressively than HTML images (depending on the browser). — Aaron, Jan 23 '14 at 21:36

score 2 · Answer 2 · answered Jan 23 '14 at 21:16

The src attribute of the element is simply passing the GET variable v to the server at the image.jpg endpoint with a value of 1390510765392. Without examining the server-side code, it is unclear why the developer is doing this. A few possibilities come to mind:

image.jpg could actually be a script (or interpreted by one) despite the .jpg extension, in which case it is possible that 1390510765392 is a resource token used to retrieve a specific image.
A frequent use of such a parameter is to simply change the src attribute without actually changing what it points at, thus invalidating any client-side (or intermediary) cache of the image and forcing it to reload, in which case the server itself likely ignores v.

score 1 · Answer 3 · answered Jan 23 '14 at 21:09

1

It allows for the name of the image to remain the same but by appending the query string it prevents browsers from using a cached version of the image. The query string essentially makes the URL "new" so the browser goes and gets what it believes to be a new resource.

answered Jan 23 '14 at 21:09

John Conde

217,595
99
455
496

1

I think calling it the "version number" is a little misleading. – j08691 Jan 23 '14 at 21:10
Only a little if at all. But since that part is not important I have removed it from the answer. – John Conde Jan 23 '14 at 21:11

score 1 · Answer 4 · answered Jan 23 '14 at 21:10

1

It's used to avoid image to be served from browser cache (because the URL is different if date changes and it makes no effect on images)

answered Jan 23 '14 at 21:10

Marcin Orlowski

72,056
11
123
141

score 0 · Answer 5 · answered Jan 23 '14 at 21:14

0

Another possabilty is to avoid flushing CDN resources when the image changes preventing the user from seeing an old version if the image.

answered Jan 23 '14 at 21:14

Lior Asta

121
3

Parameter on tag

5 Answers5