# How does OpenCV implement the Version Switcher in its Documentation?

**URL:** <https://forum.opencv.org/t/how-does-opencv-implement-the-version-switcher-in-its-documentation/14569>\
**Category:** Site Feedback\
**Tags:** documentation\
**Created:** [September 17, 2023, 1:21am UTC](https://forum.opencv.org/t/how-does-opencv-implement-the-version-switcher-in-its-documentation/14569 "2023-09-17T01:21:14Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![hwhsu1231](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.opencv.org/hwhsu1231/32/14433_2.png) [@hwhsu1231](https://forum.opencv.org/u/hwhsu1231)\
**Post date:** [September 17, 2023, 1:21am UTC](https://forum.opencv.org/t/how-does-opencv-implement-the-version-switcher-in-its-documentation/14569/1 "2023-09-17T01:21:14Z")

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Hello, OpenCV Team.

I noticed that there is a version switcher provided in [OpenCV: OpenCV modules](https://docs.opencv.org/4.x/), so that we can switch to the corresponding pages in different versions conveniently.

 ![image](https://us1.discourse-cdn.com/flex020/uploads/opencv/original/2X/3/38ccee7615acbfe64f491c67900347f63e26fb2c.png)

If possible, can someone explain its implementation? (Take CMake for example, [https://discourse.cmake.org/t/doc-versioning-mechanism/4814/3](https://discourse.cmake.org/t/doc-versioning-mechanism/4814/3))

Thanks.

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**Author:** ![berak](https://avatars.discourse-cdn.com/v4/letter/b/85f322/32.png) [@berak](https://forum.opencv.org/u/berak)\
**Post date:** [September 17, 2023, 6:39am UTC](https://forum.opencv.org/t/how-does-opencv-implement-the-version-switcher-in-its-documentation/14569/2 "2023-09-17T06:39:35Z")

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unfortunately, cmake / doxygen can only build local docs from  
exactly the code version you checked out from github, one at a time.

so, however they populate this box (no idea), it wont work without a large cache of previous doc versions on disk