Why Some Phones Accept IMEI Changes… and Others Just Don’tEver tried swapping IMEI files between two phones and got totally different results? One boots up perfectly with the new IMEI. The other? Stuck on the logo. No signal. "Null IMEI." It’s frustrating, confusing — and honestly, kind of a mystery if you don’t know what’s going on under the hood.IMEI: The Phone’s Identity CardThink of your phone’s IMEI like a national ID. It tells mobile networks who your phone is. Every phone gets a unique IMEI at the factory. If it’s missing or corrupted, you lose signal. Sometimes, your phone won't even boot properly.So yeah, it’s a big deal.Back in the Day: 2G and 3G Phones Were EasyIf you’ve worked with older phones — especially MediaTek-powered ones — you probably remember how easy it was to change the IMEI.The files that stored the IMEI were basic. No fancy protection. You could pull them from one phone, drop them into another, and things just worked. No errors, no encryption, no drama.Most of this data was stored in something called NVRAM and NVDATA. You can think of NVRAM as the permanent memory (it rarely changes) and NVDATA as the temporary one (updated more often).The system would load the IMEI from NVRAM into NVDATA every time the phone booted. So, swapping files between phones often meant instant IMEI replacement.Then Came 4G… And Things Got a Bit TougherWith 4G phones, the story started to shift.MediaTek introduced better encryption. At first, it wasn’t too bad — just a basic encryption algorithm like XOR. But soon, they moved to AES 128-bit encryption. Stronger. Smarter. Harder to crack.Still, most 4G devices didn't strictly enforce this encryption. So if the two phones were similar enough — say, same chipset, same Android version — you could still get away with copying NVRAM/NVDATA from one to the other.It was hit or miss, but many technicians found workarounds using tools like DFT or patched modems.The Real Trouble Started with 5G5G changed everything.When MediaTek launched chips like the MT6833, MT6853, MT6885, and so on, they moved from software-based IMEI protection to hardware encryption.What does that mean in plain English?It means the phone’s processor is now involved in guarding the IMEI. It checks if the IMEI matches what the chip was programmed for. If not? Boom. The phone rejects it. IMEI becomes Null, and the network is gone.In these devices, you can’t just copy files anymore. It doesn’t work. You have to go deep — using Preloader mode, BROM mode, or special tools that communicate with the processor directly.Real Example: Honor X6 vs. Honor V40Let’s say you’re working on two phones:Honor X6 (4G) — You copy NVRAM files from another Honor phone, reboot, and it works. The IMEI updates, no problem.Honor V40 (5G) — You try the same trick, and the result? "Null IMEI". Baseband gone. No signal. Total failure.Why?Because the V40 has IMEI signing and hardware-level encryption. It’s like trying to open someone else’s vault with your own key — the phone simply won’t allow it.Different Brands, Different RulesSome phone brands make this harder than others.Xiaomi, for example, used to store the IMEI in a file called LD0B_001. Now, it uses a newer, tougher file called CSSD_000. It’s deeply encrypted and tied to the hardware. You can’t edit it unless you patch the modem first.Oppo takes a different route. Its phones don’t use the same IMEI files at all. You often have to convert Oppo's encryption format from "custom" to "generic" before the phone accepts any changes.Huawei and Honor are kind of in-between. Their older 4G models are easier to work with, but their newer 5G phones are locked down tight.So… Can You Still Change the IMEI?The short answer? It depends.Here’s a quick cheat sheet:✅ Works (4G phones, no signing):You can change the IMEI by editing NVRAM or NVDATA.Tools like Getag, DFT, and RTC are helpful.Common processors: MT6765, MT6768, MT6785, MT6789❌ Doesn’t Work (5G phones with signing):You can’t just copy files.You need advanced tools and deep access.Methods include using Preloader mode, BROM mode, or META mode.Example processors: MT6833, MT6853, MT6877Real-World Fix: Oppo Reno 12F 5GLet’s say you’re fixing an Oppo Reno 12F 5G.Here’s what a successful repair might look like:Flash an old Preloader file from a 2020 firmware versionUse a tool like Pandora to patch the deviceWrite the IMEI using Reaper or similarReboot and testThat’s it. But this only works because you’re tricking the phone into thinking it’s running old firmware with less security.Final ThoughtsIf your phone accepts new IMEI files, you’re lucky. Many modern phones don’t.The reason why some work and others don’t comes down to one thing: how the IMEI is protected.Type of PhoneIMEI Change Works?WhyOlder 2G/3G Phones✅ YesNo encryption at all4G (No IMEI Signing)✅ UsuallySoftware-based security4G (Signed IMEI)⚠️ SometimesBrand protections5G Phones❌ NoHardware-level encryptionSo before you try to change or fix an IMEI, make sure you know what you're working with. Check the chipset. Know the Android version. And figure out if the phone uses signing or hardware encryption.Otherwise, you might waste hours — or worse, brick the device.