Encrypt Text & Files
Encrypt or decrypt files and text locally with a password.
Passwords and content stay in this browser. No upload is needed.
Choose files to encrypt, or drop them here.
Up to 32 MiB per file · 64 MiB per batch · 20 files
UTF-8 text, up to 1 MiB. Spaces and newlines are preserved. Empty text can also be encrypted.
Use a long, unique passphrase. Passwords are used exactly as entered, including spaces. Forgotten passwords cannot be recovered.
Choose files to get started, or switch to Text.
Results
Your results will appear here.
How it works & privacy
Contents are encrypted with AES-256-GCM and a key derived from your password using PBKDF2-HMAC-SHA256 (600,000 iterations). Every encryption uses a fresh random salt and IV. New THENC2 files authenticate their header and contents.
Metadata remains visible: the original name, file type, size and creation time are in the plaintext header. The outer download name may reveal the original name too.
Historical THENC1 files and THENC1-TEXT output remain readable within the supported limits. Their contents are authenticated, but their metadata was not authenticated. A successful legacy decryption does not prove its filename or metadata is original.
Copy encrypted text produces an armored THENC2-TEXT string for the Text tab. Download .thenc saves the same container as binary for the Files tab. File signatures are checked, so renamed encrypted files also work. Other encryption formats are unsupported.
Clear all removes passwords, drafts, files and results held by this app and revokes download URLs. JavaScript cannot guarantee secure memory erasure; clearing does not erase your clipboard or downloaded files.
These are whole-buffer operations in a cancellable worker, not streaming. Files are processed one at a time, up to 32 MiB each and 64 MiB per batch (encrypted containers may include up to 4 KiB of header overhead). Text is limited to 1 MiB. Smaller inputs may be needed on low-memory devices.
Passwords, content, filenames and results are not sent to servers or saved in browser storage. The site may send anonymous tool/event counts, subject to the existing usage privacy policy and opt-out. This is separate from local content processing. Ads and other third-party executable scripts are excluded from these two pages.
Help & FAQ — Encrypt Text & Files
How to use
- Choose Encrypt or Decrypt, then Files or Text.
- Enter or paste the content and set a strong password.
- Process your input, then copy or download the named result. Keep the password safe.
Use cases
- Encrypt notes before sending to a colleague.
- Protect short text snippets offline.
Tips & FAQs
- What algorithm is used?
- AES-GCM via the Web Crypto API with PBKDF2-derived keys.
- Is my password stored?
- The app does not save passwords. Clear all removes app-held references, but JavaScript cannot guarantee secure memory erasure.
Formats & limits
- Encrypt or decrypt text and files using AES-GCM and a password-derived key
- The .thenc header includes the original filename, MIME type and size
- Files up to 32 MiB, batches up to 64 MiB / 20 files, and UTF-8 text up to 1 MiB; smaller inputs may be needed on low-memory devices
- THENC2 authenticates headers and contents; legacy THENC1 metadata was not authenticated
Privacy
Encryption and decryption run in your browser. Copy and Download save output locally. Names, file type, size and timestamps remain visible in the encrypted container header. Anonymous site usage counts are separate from local processing.
Related tools
Updated
11 October 2026