12 years ago SD Maid 1 started on XDA, in this thread, in March 2011.
So I think it's in good tradition that SD Maid 2 does so too

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SD Maid SE (aka. SD Maid 2) is the successor to SD Maid (SD Maid 1/ SD Maid Legacy). A new app, optimized for modern Android versions, and ready for Google's future challenges 😌. Description: SD Maid SE is an open-source zero-bull**** system...
forum.xda-developers.com
I'd be thrilled if any of you would help me test it.
I promise it's not as rough around the edges as SD Maid 1's first versions

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SD Maid 2 shares some features with SD Maid 1 but not all:
Currently available are CorpseFinder, SystemCleaner, AppCleaner and AppControl.
I'm very likely re-adding a StorageAnalyzer.
Still on the fence about the Explorer and Duplicates tool.
Not planning to re-add the Searcher or Databases tool.
I want to focus on more narrow set of core tools to not spread my time too thin.
Why a new SD Maid?
I like working on SD Maid, but I'm burning out on the codebase.
All the time I could spend on improvements is drained away by adjusting to Google's ever changing requirements.
The codebase just wasn't designed for what Google requires with every new Android version.
The last major rewrite of the same magnitude was in 2015 when we went from v3 to v4.
I'm basically doing one band-aid fix after another...
I can and want to do better... I want to update the UI too, more modern, theming...
Basically tear the whole app down and rebuild it...
But SD Maid 1 has a huge user-base, of which one half would be happy about a rewrite as an update and the other half would scream in terror about me ruining the app.
They liked it the way it was.
(I personally wouldn't like it either if a dev just changed the whole app with an update.)
So the solution was obvious: A fresh start.
Write a new SD Maid, make it a separate app and let both co-exist.
People can keep using SD Maid 1 or switch to SD Maid 2 at their discretion.
SD Maid 1 will keep getting some updates (security fixes, etc.), but no new features or bug fixes related to changes in new Android versions.
You can switch to SD Maid 2/SE if you have at least Android 8, and you should probably switch if you have Android 12+.
You may also like that
SD Maid 2/SE is open source!
There is still a pro version. If you download from Google Play, you are
required to buy it, if you download from Github you are
asked to donate.
For what SD Maid needs to do, quite a lot of sensitive permissions are required.
More so with each Android update.
With all of the malicious actors in this space, I think it's prudent that apps with so much power become more transparent.
I've contemplated open-sourcing SD Maid 1 too, but for now decided against it.
It's not set up to be a "nice open source project" and the 10 years of commit history might contain swear words
towards certain companies and other things that I don't want to accidentally publish

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