Security

File Encryption

Encrypt and decrypt any file with a password in the browser using AES-256-GCM authenticated encryption and PBKDF2 key derivation, with built-in integrity verification, password strength feedback, and a chunked progress bar. Suitable for archiving sensitive documents, moving files across devices, adding a protective layer before cloud uploads, and delivering password-protected files to teammates or clients.

  • AES-256-GCM authenticated encryption rejects any tampered ciphertext instead of silently producing garbled output
  • PBKDF2-SHA-256 derives a 256-bit key from your password, with a unique random salt and IV for every file
  • Streaming chunked processing with a live progress bar handles hundreds of megabytes of video, archives, and database dumps reliably
  • Everything runs inside the browser tab: files and passwords never leave your device and disappear when you close the page
  • Ciphertext is self-describing, so decryption never asks you to remember the algorithm, parameters, or original filename
  • Live password strength feedback flags weak choices, and encryption requires a second confirmation to avoid typos
tools/File Encryption
No file selected

Your password is the only key. Store it in a password manager — there is no recovery path if it is lost.

Files, passwords, and key derivation all stay inside this browser tab and are released when the page closes.

Keep a backup of the original file until you confirm the ciphertext decrypts back to it.

Waiting

The encrypted or decrypted file will appear here when ready

AES-256-GCM · PBKDF2-SHA-256 · 200,000 iterations
AES-256-GCM
PBKDF2-SHA-256 · 200,000 iterations
Encryption commands

Overview

A local-first encryption workspace that wires together passwords, key derivation, AES-256-GCM authenticated encryption, and download — so encrypting a file becomes a repeatable, verifiable habit instead of a guessing game.

  1. 01

    AES-256-GCM authenticated encryption

    Files are encrypted with AES in GCM mode using a 256-bit key. Each ciphertext carries an authentication tag, so any tampering with the bytes is detected and rejected instead of silently decrypted into corrupted data.

  2. 02

    PBKDF2 password-based key derivation

    Passwords pass through PBKDF2-SHA-256 with 200,000 iterations to produce a 256-bit key. Each file gets its own random salt, which raises the cost of offline brute-force or rainbow-table attacks.

  3. 03

    Streaming chunked processing

    Encryption and decryption proceed in 4 MB chunks instead of loading the whole file into memory. Hundreds of megabytes of video, archives, virtual disks, and database dumps remain practical.

  4. 04

    Live progress feedback

    Progress updates after every chunk, so long-running tasks always show movement. Any in-flight job can be cancelled cleanly without leaving the page in a stuck state.

  5. 05

    Self-describing ciphertext

    The output header carries a magic number, version, salt, IV, chunk size, and original filename. Decryption never asks you to remember which algorithm or parameters were used.

  6. 06

    Password strength feedback

    A live strength meter rates passwords based on length, character variety, and known weak patterns, encouraging longer and more varied passphrases before encryption begins.

  7. 07

    Confirmation and safe resets

    Encryption requires a confirmation field so a typo cannot lock you out of a freshly encrypted file. Files, passwords, and results can be cleared and restarted at any time.

  8. 08

    Local-only processing

    File reading, key derivation, encryption, decryption, and the download link all happen inside the current browser tab. Nothing is uploaded, logged, or relayed through a third-party server.

How to use

Drop a file in, type a password, and press Encrypt or Decrypt. Everything runs locally and the result is downloaded straight from the browser.

  1. 01

    Choose Encrypt or Decrypt at the top of the workspace. If you are unsure, files produced by this tool use a .dkl suffix.

  2. 02

    Drop a file into the upload zone, or click to browse. Only the file size and type are read at this point — no encryption has started yet.

  3. 03

    Type your password. For encryption, aim for 12+ characters mixing cases, digits, and symbols, and retype it in the confirmation field.

  4. 04

    Press Encrypt file or Decrypt file. The progress bar shows the current chunk and the job can be cancelled at any time.

  5. 05

    Download the result. Encrypted output gets a .dkl suffix, and decrypted output restores the original filename stored inside the ciphertext header.

  6. 06

    Verify immediately: decrypt the fresh ciphertext with the same password to confirm it round-trips before deleting any intermediate copies.

Details

File encryption is only as strong as its weakest detail. The choices below cover algorithm, key derivation, random parameters, authentication, and implementation quality.

  • Keys are not derived by truncating the password — PBKDF2-SHA-256 stretches it through 200,000 iterations into a 256-bit key, and each file gets its own random salt so the same password produces completely different ciphertexts.
  • The initialization vector (IV/nonce) is generated by the Web Crypto secure random source on every encryption, eliminating catastrophic key-IV reuse weaknesses.
  • AES-GCM authenticated encryption attaches a 128-bit tag to each chunk; any modification to ciphertext, IV, or header bytes causes decryption to fail loudly instead of returning corrupted data.
  • The ciphertext header records a DKL1 magic number, a format version, the salt, the IV, the chunk size, and the original filename, so decryption is parameter-free for the user.
  • All cryptographic primitives come from the browser-provided Web Crypto API, avoiding bundled third-party crypto implementations and their wider attack surface.
  • Encryption and decryption stream chunk by chunk; the progress bar and cancel control keep large jobs interactive instead of blocking the tab for minutes.
  • Passwords are never persisted to localStorage, IndexedDB, or the clipboard, and no telemetry beacon is sent during the workflow.
  • There is intentionally only one algorithm combination — no legacy DES, ECB mode, or self-rolled ciphers — to remove the risk of accidentally choosing a weak option and to keep the ciphertext format consistent over time.

Use cases

Day to day this tool covers two recurring needs: "encrypt this file before sharing it" and "open an encrypted archive I made earlier".

  1. Sensitive document archival

    Wrap pay stubs, contracts, ID scans, customer lists, and operational data into .dkl ciphertexts before saving to local or cold-backup drives, so a lost backup disk does not equal a leaked dataset.

  2. Cross-device transfer

    When sending a file through chat, email, fast-relay file transfer, or a USB stick, encrypt first and share the password through a separate channel — the transport itself no longer controls the content.

  3. Pre-cloud upload protection

    Add end-to-end encryption before uploading to Google Drive, OneDrive, Dropbox, iCloud, or any object storage bucket, so even a provider-side scan or breach only exposes ciphertext.

  4. Internal team distribution

    Encrypt confidential drafts, manuscripts, source code, or training material before sharing the link, then deliver the password through a separate secure channel to limit the blast radius of a forwarded URL.

  5. Repair and device handover

    Before sending a laptop in for repair, selling a second-hand device, or recycling an old drive, encrypt the files you cannot wipe completely so that technicians or next owners cannot read their contents.

  6. Backups and the cold archive

    Maintain an "encrypted drawer" for long-term archives — old project assets, photo libraries, mail archives — so cold data quietly stays unreadable to anything but the password holder.

  7. Pre-release confidential material

    For embargoed press releases, earnings reports, or design drafts, share encrypted copies during internal and external review so no draft is exposed by an intermediate hop.

  8. Legal and compliance retention

    Keep evidence, contract attachments, customer-complaint recordings, and audit materials encrypted alongside your access control rules to align with data-minimization and access-restriction expectations.

See also

If you only need to confirm a file was not altered in transit and secrecy is not a goal, use Hash Generator to compute a SHA-256 or BLAKE3 digest as a lightweight integrity check. Before encrypting, reach for Password Generator to mint a high-entropy passphrase instead of relying on a memorable but weak one. If the file is going to be shared or uploaded somewhere, run it through EXIF Remover first to strip EXIF, GPS, camera-model, and editing metadata that would otherwise leak identity and location even when the contents are encrypted.

Best practices

Strong encryption is only the foundation. Passwords, key custody, backups, and distribution decide whether a file is actually protected.

  • Use at least 12 characters mixing uppercase, lowercase, digits, and symbols. Avoid reusing common-site passwords or easily-guessed phrases.
  • Store each file password in a password manager such as 1Password, Bitwarden, or KeePass — never on a sticky note or inside chat history.
  • Send the password and the ciphertext through different channels. If the ciphertext was emailed, share the password by phone, SMS, or in person.
  • Decrypt the freshly created ciphertext once to confirm it round-trips before deleting the original file or uploading to cloud storage.
  • Keep two copies of critical encrypted files on separate physical media so a single-device failure does not wipe out the ciphertext as well.
  • Avoid reusing the same password across many files. If it leaks, every file protected by it leaks too.
  • After using a shared or public computer, clear the browser tab and the downloads folder so no leftover ciphertext or files remain.
  • For teams, manage file passwords inside a shared password-manager vault with audit logs, so it is always clear who retrieved which password and when.

Limitations

Encryption is one slice of data security. Knowing its boundaries keeps it from being treated as a universal shield.

  • Your password is the only key. If it is forgotten there is no backdoor, password reset, or recovery flow that can return the file contents.
  • This tool does not provide key escrow, password recovery, shared decryption, expiration, or revocation. For those, look at enterprise KMS, DRM, or file-collaboration platforms.
  • Encryption protects confidentiality and integrity of files at rest. It cannot prevent an already-authorized reader from screenshotting, copying, or forwarding the content.
  • The ciphertext filename is informational. Attackers can still infer signals from file size, modification time, and directory location.
  • Browser memory limits cap the size of a single file you can process. For multi-gigabyte files, prefer a desktop tool or server-side workflow.
  • There is only one supported algorithm combination. Ciphertexts created with future versions may not open in older clients, so keep the matching tool version alongside long-term archives.
  • The tool cannot tell that a ciphertext you received is the same one that was originally produced. Distribute ciphertexts and passwords through trusted channels.
  • Encryption does not substitute for digital signatures or legal non-repudiation. Use dedicated signing or timestamping services when those properties are required.

FAQ

Practical answers about the algorithm, password handling, ciphertext format, limits, and local-only processing.

Which algorithm does this file encryption tool use?

AES-256-GCM authenticated encryption, with the key derived from your password via PBKDF2-SHA-256 over 200,000 iterations. Every file uses an independent random salt and IV, which defeats common offline dictionary attacks and replay-style ciphertext swaps.

Why is there no choice of algorithm?

AES-256-GCM is a widely trusted authenticated encryption primitive, and a single carefully chosen parameter set is safer than a long menu. Multiple options increase the chance of picking a weak combination and fragment the ciphertext format across versions.

Are my files uploaded anywhere?

No. File reading, key derivation, AES-GCM processing, and the download link all happen inside this browser tab. Even for hundreds of megabytes of data, the original file, the ciphertext, and the password never leave your device.

I forgot the password — can I recover the file?

No. Symmetric password-based encryption is built so that nobody (including us) can decrypt the file without the password. Store passwords in a password manager and confirm you can read them back before relying on them.

How much bigger does the file get after encryption?

Usually only a few dozen to a few hundred extra bytes, covering the header, salt, IV, original filename, and per-chunk authentication tag. For typical multi-megabyte files the size change is effectively invisible.

Decryption says the password is wrong or the file is not encrypted by this tool — now what?

First retype the password, including case and any leading or trailing spaces. Then confirm the ciphertext file is complete — chat apps and email sometimes recompress attachments. If the file came from a different tool, decrypt it with the matching tool instead.

Can I encrypt very large files such as multi-gigabyte videos?

The tool processes data in 4 MB chunks and can stream through fairly large files, but a single browser tab is still bounded by memory limits. For multi-gigabyte archives, a desktop tool or server-side encryption is more appropriate.

Does encryption protect against deletion or ransomware?

No. Encryption defends confidentiality and integrity, but it cannot stop devices from being physically destroyed, overwritten by ransomware, or remotely wiped. Reliable data protection combines encryption with backups, endpoint defense, and access control.

Is it okay to use the same password for many files?

Technically yes, but it is not advised. A single password leak then exposes every file protected by it. Use separate passwords for different classifications and let a password manager keep track of them.

Related tools

Beyond encryption, integrity hashing, strong password generation, and signing utilities round out the workflow.