Tuxia Learn · ~5 min read
Why do WeChat / QQ "wash away" hidden files?
Nine times out of ten, a Tuxia extraction failure has the same cause: the image was compressed or transcoded on its way, and Tuxia reports "not a Tuxia file, or the image was compressed / transcoded". That's not a bug — it's the inborn weakness of append-style steganography. This article explains the why and the fix, once and for all.
Why platforms compress your images
Simple: money. A phone original is several MB; at billions of images a day, storing and transmitting originals would cost a fortune in bandwidth and storage. So chat apps shrink dimensions, lower quality and re-encode by default, squeezing megabytes into hundreds of KB. Your eyes barely notice — but the file has been "rewritten".
How compression kills hidden data
Tuxia appends files after the image end marker (PNG's IEND, GIF's 0x3B). Re-encoding only cares about "the picture itself" — everything after the end marker is discarded as junk, and transcoding to JPG rewrites all pixel data. Result: the picture looks the same, the hidden data is gone.
Remember this: any image that got "smaller / looks recompressed" has lost its hidden data. Conversely, a byte-identical original keeps it safe.
How to send and keep the original
- WeChat: in the chat tap "+" → "Files" → "Photos", and send as a file (not via "Photos" directly); or use "File Transfer" to send files;
- QQ: same — send as a "File", not as an "Image";
- Reliable general options: zip it first, share a cloud-drive link, email attachment, Bluetooth / AirDrop / USB cable;
- Forums: publish using the "original image" or "original link" option, not the platform's compressed upload.
These are the general patterns — platform policies change anytime (WeChat has adjusted its original-image logic before). The safest habit: have the recipient try extracting in Tuxia first, and only delete your source file after it works.
Received an image? Do these two checks
- Check the file size: if it's much smaller than what the sender described, it was almost certainly compressed — ask them to resend as a file;
- Just open it in Tuxia and try extracting: success means it's the original; an error means it was transcoded — don't keep retrying passwords, that's not the problem.
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