Install Android 15 on Galaxy A21s (CrDroid OS) – How to Guide!

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Want to install Android 15 on your Samsung Galaxy A21s? You are in the right place. This comprehensive, step-by-step guide walks you through the complete process of flashing the unofficial LineageOS 22 custom ROM on the Samsung Galaxy A21s (codename: a21s).

Even though Samsung has ended official software support for the Galaxy A21s (which shipped with Android 10 and received Android 12 as its final update), you can breathe new life into this Exynos 850-powered device with Android 15. This custom ROM delivers the latest Android features, improved performance, better battery optimization, enhanced privacy controls, and a clean AOSP stock Android experience.

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Why Install Android 15 on Galaxy A21s?

The Samsung Galaxy A21s (released June 2020) was a popular budget smartphone powered by the Exynos 850 processor with up to 6GB RAM and a large 6.5-inch PLS LCD display. Despite being a capable device, Samsung ended official software support at Android 12 (One UI 4.1), leaving users stuck on outdated software with potential security vulnerabilities.

Installing Android 15 via CrDroid OS gives your Galaxy A21s a second life with:

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Latest Security Patches
Protection against current known vulnerabilities and exploits.
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Better Performance
AOSP-based ROMs are usually leaner and faster than stock firmware.
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Extended Battery Life
Android 15 power optimizations can improve battery efficiency.
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Modern App Support
Run newer apps that require recent Android API levels.
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Android 15 Key Features You'll Get on Galaxy A21s

Android 15 on Galaxy A21s with CrDroid OS delivers a modern Android experience. Android 15 focuses on stability, privacy controls, and performance tuning. These are the key improvements you can expect from this update:

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Private Space

Sensitive apps can stay isolated behind an extra unlock boundary for improved privacy.
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Faster App Launch

Runtime and system optimizations reduce lag and improve app responsiveness.
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Background Efficiency

Smarter process handling lowers unnecessary battery drain in idle and standby states.
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Media and Audio Upgrades

Improved media pipeline behavior and cleaner handling for playback and recording tasks.
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Security Hardening

Stronger platform-level protections and safer defaults for modern apps.
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Refined System UI

Polished UX details across notifications, quick settings, and platform interactions.
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Important Warnings — Read Before Installing Android 15

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Device-specific ROM: This Android 15 custom ROM is ONLY for the Galaxy A21s. Do not flash it on any other device — it will brick your device.

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Brick risk: Carefully follow every step in the correct order. Incorrect installation — such as flashing the wrong file, interrupting the process, or skipping the wipe — can permanently brick your Galaxy A21s. TheUpgradeGuide is not responsible for any damage.

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Complete data wipe: Installing this custom ROM erases everything on your Galaxy A21s — apps, photos, contacts, messages, and files. Create a complete backup before proceeding.

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Battery requirement: Charge your Galaxy A21s to at least 50–60% before starting. An accidental shutdown during the flashing process can leave your device in a non-bootable state.

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Warranty void: Unlocking the bootloader and installing a custom ROM will void your manufacturer warranty.

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Pre-Installation Requirements for Galaxy A21s

Make sure you have all of the following ready before starting the Android 15 installation on your Galaxy A21s:

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Unlocked bootloader: Your Galaxy A21s must have an unlocked bootloader. Use Xiaomi’s official Mi Unlock Tool if you haven’t done this. The process requires linking your Mi account and waiting approximately 7 days.

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TWRP Recovery installed: You must have TWRP Recovery installed on your Galaxy A21s. Watch TWRP installation tutorial for Galaxy A21s →

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Full data backup: Back up all important data — photos, contacts, messages, app data, WhatsApp chats, and files — before starting the installation. Consider using Google Backup and Google Photos for cloud backup.

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USB drivers installed: Install the appropriate USB drivers on your PC/Mac. These are needed if you’re using ADB/Fastboot for any part of the process.

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XDA Forum Thread: CrDroid OS for Galaxy A21s — XDA Forum →

Always check this XDA Forum thread for the latest build updates, known bugs, required patches, firmware requirements, and community feedback before installing.

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Download Android 15 ROM & GApps for Galaxy A21s

CrDroid OS ROM (AOSP-Based Android 15) for Galaxy A21s

Google Apps (GApps) for Android 15 ARM64 – Choose One Package

apps LiteGApps (Android 15 ARM64)apps NikGApps (Android 15 ARM64)apps MindTheGApps (Android 15 ARM64)apps BiTGapps (Android 15 ARM64)

search Not sure which GApps to pick? Read our complete GApps compatibility guide ->

bolt Quick Installation Overview

Short on time? Here’s the 5-step summary of how to install Android 15 on your Galaxy A21s. Scroll down for the detailed guide with screenshots.

  1. 1Download the CrDroid OS Android 15 ROM & GApps for Galaxy A21s.
  2. 2Boot your Galaxy A21s into TWRP custom recovery mode.
  3. 3Wipe system, vendor, data, cache, and dalvik cache partitions.
  4. 4Flash the Android 15 ROM zip followed by the GApps zip via TWRP Install.
  5. 5Wipe cache, reboot, and enjoy Android 15 on your Galaxy A21s!
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Step-by-Step: Install Android 15 on Galaxy A21s

1

install_mobile Install TWRP Custom Recovery on Galaxy A21s

The first step is to install TWRP (Team Win Recovery Project) custom recovery on your Galaxy A21s. TWRP replaces the stock recovery and allows you to flash custom ROMs, GApps, and create complete system backups. You’ll need a PC/Mac with ADB and Fastboot tools installed, plus a USB cable. If TWRP is already installed on your Galaxy A21s, skip directly to Step 2.

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file_copy Transfer the ROM and GApps Files to Your Galaxy A21s

Download the Android 15 CrDroid OS ROM zip and your preferred GApps package from the download section above. Connect your Galaxy A21s to your computer via USB and transfer both .zip files to the device’s internal storage root folder or SD Card. Remember the file location — you’ll need to find these files in TWRP later.

Transfer Android 15 CrDroid OS ROM and GApps zip files to Galaxy A21s internal storage via USB
3

restart_alt Boot Galaxy A21s into TWRP Recovery Mode

Disconnect the USB cable and power off your Galaxy A21s completely. Once the device is off, press and hold the Power button + Volume Up button simultaneously until you see the TWRP logo appear on screen. Release both buttons when TWRP loads. If prompted, swipe to allow modifications.

Boot Galaxy A21s into TWRP Recovery Mode using Power and Volume Up buttons
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backup Create a Nandroid Backup of Your Current ROM

This step is critical for safety. In TWRP, tap Backup and create a complete Nandroid Backup. This creates a bit-for-bit copy of your entire current system — including the ROM, apps, data, and settings. If anything goes wrong during the Android 15 installation, or if you want to return to your previous ROM, you can restore this backup in minutes.

Detailed Nandroid Backup guide →

Create a full Nandroid Backup in TWRP before installing Android 15 on Galaxy A21s
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delete_sweep Perform a Factory Reset Using Advanced Wipe

Now perform a thorough Factory Reset to prepare your Galaxy A21s for the Android 15 ROM. In TWRP, navigate to Wipe → Advanced Wipe. Check the boxes for Cache, Dalvik Cache, System, and Data partitions. Then Swipe to Wipe. This completely clears the old system files, user data, and cache — preventing conflicts with the new Android 15 ROM.

TWRP Advanced Wipe selecting Cache, Dalvik, System, and Data partitions on Galaxy A21s
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home Return to the TWRP Main Menu

After the wipe completes successfully, navigate back to the TWRP Main Menu by tapping the back arrow or pressing the home/center navigation button on your Galaxy A21s. You should see the main TWRP screen with options like Install, Wipe, Backup, Restore, etc.

Navigate back to TWRP Main Menu on Galaxy A21s after factory reset
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system_update Flash the Android 15 ROM (CrDroid OS)

This is the main step. From the TWRP Main Menu, tap Install. Navigate to the folder where you saved the CrDroid OS (Android 15) ROM zip file. Tap the file to select it, then Swipe to Confirm Flash. The flashing process takes 2–5 minutes — do not touch anything or power off your Galaxy A21s until it completes. You’ll see “Successful” when done.

Flash Android 15 CrDroid OS custom ROM zip file via TWRP Install on Galaxy A21s
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apps Flash the Google Apps (GApps) Package

Immediately after the ROM flash completes, do not reboot yet. Instead, tap “Install” again (or use the back button), navigate to your GApps zip file, and flash it the same way. This installs the Google Play Store, Gmail, Google Maps, YouTube, and other essential Google services on your Galaxy A21s. Without GApps, you won’t have access to Google services or the Play Store.

Flash GApps package via TWRP immediately after Android 15 ROM on Galaxy A21s
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cached Wipe Cache and Dalvik Cache

After the GApps flash completes, you’ll see a “Wipe cache/dalvik” button at the bottom left of the TWRP screen. Tap it and Swipe to Wipe. This clears any residual cached data and ensures a clean, error-free first boot of Android 15 on your Galaxy A21s. Skipping this step can cause boot loops or app crashes.

Wipe cache and dalvik cache in TWRP after flashing Android 15 ROM and GApps on Galaxy A21s
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restart_alt Reboot Your Galaxy A21s into Android 15

After the cache wipe completes, Press the Home Button, Click Reboot button from the main menu, Tap on System and Swipe to Reboot. Your Galaxy A21s will now boot into Android 15 (CrDroid OS) for the first time! Important: The first boot typically takes 5–10 minutes as the system optimizes all applications. The screen may appear stuck on the boot animation — this is completely normal. Do not force restart during this process.

Reboot Galaxy A21s into Android 15 CrDroid OS - first boot after successful custom ROM installation
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Android 15 Successfully Installed on Your Galaxy A21s!

Congratulations! You’ve successfully installed Android 15 (CrDroid OS) on your Galaxy A21s. Enjoy the latest Android features, improved performance, enhanced security, and a clean stock Android experience on your refreshed device!

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What’s Working & Not Working on Android 15 (Galaxy A21s)

Based on the XDA Forum thread and community reports, here’s the current status of features on the CrDroid OS (Android 15) ROM for the Galaxy A21s. Note: This may vary between builds, so always check the latest forum post.

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  • ✅ Phone calls & SMS
  • ✅ Wi-Fi & Hotspot
  • ✅ Mobile data (4G LTE)
  • ✅ Bluetooth & audio
  • ✅ Camera (photo & video)
  • ✅ GPS & location
  • ✅ Fingerprint sensor
  • ✅ NFC

cancel Known Issues

  • ⚠️ Minor camera quirks in some modes
  • ⚠️ Some hardware features may vary by build

Always check the XDA Forum thread for the most up-to-date bug list for your specific build version.

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Troubleshooting Common Issues

🔄 Stuck on Boot Animation (Bootloop)

If your Galaxy A21s is stuck on the boot animation for more than 15 minutes, it may be bootlooping. Reboot into TWRP (Power + Vol Up), perform a full wipe (System, Data, Cache, Dalvik), and re-flash the ROM and GApps. Make sure you’re using compatible GApps for Android 15 arm64.

❌ “Error 7” or “Zip Verification Failed”

This usually means you’re flashing a ROM not built for your device. Double-check that the ROM zip is specifically for the Galaxy A21s. Also ensure your TWRP version is up-to-date and compatible with Android 15 ROMs.

📱 No Mobile Data or Signal After Installation

You may need to flash the correct firmware (baseband/modem) before installing the ROM. Check the XDA Forum thread for the recommended firmware version for your build of CrDroid OS.

🔙 How to Restore Back to Stock ROM

If you want to go back to the stock ROM: (1) restore your Nandroid Backup via TWRP → Restore, or (2) download the official stock ROM from the manufacturer and flash it using the appropriate flash tool on your PC. This will completely restore your Galaxy A21s to factory stock condition.

Frequently Asked Questions — Android 15 on Galaxy A21s

Here are answers to the most commonly asked questions about installing and using Android 15 (CrDroid OS) on the Galaxy A21s:

Is the Android 15 ROM for Galaxy A21s stable enough for daily use?

The CrDroid OS (Android 15) ROM for the Galaxy A21s is an unofficial build. Core features — including phone calls, Wi-Fi, mobile data, camera, Bluetooth, GPS, and the fingerprint scanner — work well in most builds. Some minor bugs may exist depending on the build version. We recommend checking the XDA Forum thread for the latest known issues before installing it as your daily driver.

Will installing a custom ROM void my Galaxy A21s warranty?

Yes, unlocking the bootloader and installing a custom ROM voids the manufacturer warranty. However, since the Galaxy A21s was released in September 2019, virtually all units are well past their warranty period, so this shouldn’t be a concern for most users.

Can I go back to stock ROM after installing Android 15 on my Galaxy A21s?

Absolutely. You have two options: (1) Restore your Nandroid Backup through TWRP Recovery to return to your exact previous ROM state, or (2) Download the official stock ROM from the manufacturer’s website and flash it using the appropriate flash tool to perform a clean restore to stock firmware.

Which GApps package should I use with Android 15 on Galaxy A21s?

You can choose from four popular options: LiteGApps (recommended for minimal footprint), NikGApps (offers granular control over which Google apps to install), MindTheGApps (balanced package), or BiTGapps (lightweight alternative). All must be the ARM64 variant for Android 15 (API 35). Read our complete GApps compatibility guide to choose the best option for your needs.

Do I need an unlocked bootloader to install Android 15 on Galaxy A21s?

Yes, an unlocked bootloader is a mandatory prerequisite. Without it, you cannot install TWRP Recovery or flash any custom ROM. Use the manufacturer’s official unlock tool to request a bootloader unlock. The process typically involves a waiting period before the unlock is approved.

Does the Android 15 ROM support the Galaxy A21s’s fingerprint scanner?

Yes, in most CrDroid OS builds for the Galaxy A21s, the fingerprint scanner works correctly. However, functionality can occasionally vary between different build versions. If the fingerprint scanner isn’t working after installation, try updating to the latest build or check the XDA Forum for any required patches.

How do I update the Android 15 ROM on my Galaxy A21s after installation?

To update to a newer build of CrDroid OS: Download the latest ROM zip from the LineageOS download page, transfer it to your device, reboot into TWRP, and flash the new ROM zip over the existing installation (this is called a “dirty flash”). Then wipe cache/dalvik and reboot. A full data wipe is usually not needed for minor updates, but always check the XDA thread for update-specific instructions.

Is the Xiaomi Mi CC9 the same as the Galaxy A21s for custom ROM installation?

Yes, the Xiaomi Mi CC9 and Galaxy A21s are the same hardware device sold under different names in different regions. The Mi CC9 was the Chinese variant, while the Galaxy A21s was the global/international variant. Both use the exact same ROM, TWRP recovery, firmware, and kernel files. You can follow this same guide for either device.

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Have questions or ran into issues while installing Android 15 on your Galaxy A21s? Drop a comment below and we’ll help you out! You can also get support from the XDA Forum community where the ROM developer and experienced users actively respond to questions.