The choice of whether or not to convert YouTube content into MP3 format is yours, and your ability to do so may depend upon your choice of YouTube to MP3 app Android can run for that task. But there are also other ways to proceed with this conversion, depending on your needs.
Check Download Permission
Before choosing either an app or a browser workflow, it’s important to check the authorization: Do you own the material? Is there an appropriate license for what you’re doing, or have you explicitly authorized a download? Can you legally play back public content, search through it, or place it in a chart? If you can’t, then it doesn’t mean that you can download it without the proper rights. Download permission must come from the rights holder; public playback alone doesn’t grant it.
There is at least one documented Android candidate that may be useful. YTDLnis documents an open source audio/video downloader for Android 7.0 and above. While the developer has stated what this particular application does, it isn’t clear from the description how successful it will be at converting a particular YouTube upload to MP3 format.
The two listings appear similar at first glance, but the name “Google Play” is somewhat misleading because Google plays only the role of host; the app itself has no connection to Google, unless it were somehow tied to YouTube’s API as well. It’s possible, however, that this app might actually work as expected. The listing title is a bit confusing because MP3 files exist within Android and its apps, but they’re not limited to those formats. Its stated formats are video formats, without explicit MP3 conversion support.
Uptodown offers a similar listing, but again, the app name doesn’t tell you whether it will convert YouTube videos into MP3 format, or if it’ll convert them to something else entirely. In fact, it appears that the Uptodown version simply redirects to a website with the same name, suggesting a different workflow than what’s described above.
APK Signing Identity and Requested Access
The problem with evaluating the provenance of an APK file lies in the distinction between signing identity and safety, and historical listing details versus present-day compatibility or permission necessity. You can verify both the signing certificate of an app, along with the signing-certificate SHA-256, against the developer repository for additional information about their trusted download links. Other sources of YTDLnis are explicitly disclaimed by the developer, nor should they be assumed safe.
While we don’t know who signed the APK file, we can compare it to the signing identity used by our previous research, which was:
SHA-256: 263645cb5272eb290759fe1f59149ae24df6ce171e9f6666eead981d3fc64c95
Uptodown lists YouTube To MP3 converter version 9.1, dated November 29, 2018, from Ahad Ali Inc. Keep in mind that this isn’t the same app, though.
When evaluating APK files and their requested access, it’s important to keep in mind that the signing identity doesn’t prove safety, though a mismatch with the documented signature indicates a modified app. We include these details simply to provide you with background information, nothing more. Uptodown lists eight unnamed permissions; that count doesn’t establish necessity. Check for unrelated access and credential requests.
Browser Conversion Options
If you choose to use Ytmp3 as an occasional authorized download option, it will function similarly to many of the web-based services that allow users to convert YouTube videos into MP3 format. However, this service is only available if your phone has mobile-browser support (i.e., if you have internet connectivity). Saving behavior depends on your browser and device. Also, the availability of conversions relies on both the upload and conversion provider, which is often dictated by the platform itself.

Ytmp3’s video-title wording isn’t sufficient to establish conversion availability; equivalent Android behavior for Free YT to MP3 hasn’t been established. Check explicit documentation of Android compatibility and MP3 output before choosing it.
However, account credentials needn’t be entered in the process of converting a YouTube video. A quick test suggests that you won’t be prompted to enter a password, just a YouTube username. And that, alone, shouldn’t worry you.
Download Paths and Saved Files
In YTDLnis, you can choose a playlist download path and open or share files from a finished notification. Browser downloads commonly reach Downloads; a saved file isn’t necessarily a music-library entry.