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Frequently Asked Questions
Everything you need to know about Stegg and steganography
Important: Image Compression
Most social media and messaging apps compress images, which destroys hidden data. Always share stegged images as files (not photos) or use AirDrop, email, or cloud storage.
What is steganography?
Steganography is the practice of hiding secret data inside ordinary-looking files. Stegg uses LSB (Least Significant Bit) steganography to hide messages in the pixels of an image. The image looks completely identical to the human eye — only Stegg can reveal what's hidden inside.
Why does Stegg output PNG images?
PNG is a lossless image format, meaning every pixel is preserved exactly as-is. JPEG and other lossy formats change pixel values during compression, which destroys the hidden data. Stegg always outputs PNG to ensure your secret messages remain intact.
Will my message survive if I send the image via iMessage or WhatsApp?
It depends! Many messaging apps re-compress images, converting them to JPEG, which destroys hidden data. For reliable delivery:
✅ Send as a file/document attachment (not photo)
✅ Use AirDrop (preserves original PNG)
✅ Use email attachments
✅ Upload to cloud storage (Google Drive, iCloud)
✅ Use "Resilient Mode" for mild compression
❌ Sending as a regular photo in iMessage/WhatsApp may compress it
What is "Resilient Mode"?
Resilient Mode uses 2 bits per color channel instead of 1, making the hidden data more resistant to mild image compression or quality loss. The tradeoff is that the image may show very subtle visual artifacts and the capacity is the same but data recovery is more reliable.
Use Resilient Mode when:
- The image might get mildly re-saved or converted
- You want extra safety for important messages
Note: Even Resilient Mode cannot survive aggressive JPEG compression. Always send as PNG when possible.
How much text can I hide?
It depends on the image size. Each pixel can hide 3 bits of data (one in each color channel). A 1000×1000 image can hide about 375 KB of text — that's roughly 375,000 characters, or about 60,000 words! Stegg also compresses your message before hiding it, so you can often fit even more.
Is the password encryption secure?
Stegg uses XOR encryption with key derivation from your password. This provides reasonable privacy for casual use — it prevents someone from simply running Stegg on the image to read your message. For truly sensitive data, we recommend also encrypting your message before hiding it in Stegg.
Can someone detect a stegged image?
To the human eye, a stegged image looks identical to the original. However, statistical analysis tools (steganalysis) can sometimes detect that LSB steganography was used. For casual privacy, Stegg is excellent. For high-security use cases, consider additional layers of protection.
What is "Hide Image in Image"?
This premium feature lets you hide an entire photo inside another photo. The cover image looks completely normal, but contains a secret image that only Stegg can reveal. The secret image is compressed and embedded in the pixels of the cover image. The cover image needs to be significantly larger than the secret image to have enough pixel capacity.
Do screenshots work?
No. Taking a screenshot of a stegged image will not preserve the hidden data. Screenshots re-render the image to your screen's pixel grid and apply compression, which destroys the LSB data. Always share the original file.