Need to lock a sensitive document before you email it or park it in cloud storage? This file encrypter decrypter is an online tool for encrypting and decrypting files with a password. It uses AES-256 so you can encrypt files and decrypt files in a few clicks, with no software installation and no crypto knowledge required. Your password becomes the key, and your browser does all the work.
How a File Encrypter Decrypter Turns a Password into a Key
Every tool of this kind has to solve one problem: a human password is short and predictable, while an encryption key must be long and random. The answer is key derivation. Your password goes in, a long encryption key comes out, and that key is what actually scrambles the file. The same secret key is regenerated later when you decrypt, which is why this design is called symmetric encryption: one key handles both encryption and decryption. The free text to nato alphabet converter converts your input instantly, right in your browser.
Key Derivation with PBKDF2
The tool runs your password through PBKDF2 with HMAC-SHA256, a random salt, and 600,000 iterations. The salt is a fresh random value for every file, so two files protected with the same passkey still receive different keys. The iteration count is the part that defends you against brute-force guessing, because every guess an attacker makes has to repeat the hash 600,000 times.
$$\text{key} = \text{PBKDF2}(\text{password},\ \text{salt},\ 600{,}000)$$
That slowdown is easy to quantify. If an attacker could test 10 billion raw hashes per second, key stretching divides that speed by the iteration count:
$$\text{guesses per second} = \frac{10{,}000{,}000{,}000}{600{,}000} \approx 16{,}667$$
The figure below shows the same arithmetic, and the 10 billion speed is an assumption for illustration rather than a measured benchmark.
AES-GCM Authenticated Encryption
Once the key exists, AES-GCM does the heavy lifting. GCM is a mode of authenticated encryption: it scrambles the data for confidentiality and also attaches a 16-byte tag that proves nothing changed. A random 12-byte IV (initialization vector) makes sure identical files never produce identical ciphertext. This is AES file encryption in its modern form. Some command-line programs use CBC mode instead, which hides the content but has no built-in authentication, so GCM is the stronger default for everyday protection.
Encrypt File Online in Four Steps
You can encrypt a file in under a minute, whether it is a tax return, a scan, or a folder of photos packed into one archive. The steps below follow the same flow as most pages like this one, so they will feel familiar if you have used one before. Pick a modern browser and there is nothing to install. The password phonetic readout runs entirely in your browser — nothing you enter is ever sent to a server.
- Choose the file. Click the upload area or use drag & drop to pick documents, images, PDFs, or text files.
- Enter a password and type it a second time to catch typos. Nothing is recoverable without it.
- Click Encrypt. Processing happens on your device and takes a second or two for a few megabytes.
- Download the encrypted output. It is a new file with an .enc extension, and your original file stays untouched.
Here is a worked example. You encrypt tax-return-2025.pdf, which is 3,847,216 bytes, with the password mapleRidge42. The result is slightly larger because the tool stores the 16-byte salt, the 12-byte IV, and the 16-byte authentication tag alongside the ciphertext:
$$\text{encrypted size} = 3{,}847{,}216 + 16 + 12 + 16 = 3{,}847{,}260\ \text{bytes}$$
That 44-byte difference is all the metadata the file needs to be decrypted later, which is why the encrypted file is almost exactly the size of the original. Large files encrypt just as easily, since AES is built for speed.
Decrypt File Online and Fix Common Decryption Errors
To decrypt a file, upload the .enc file, enter the exact password you used before, and click Decrypt. The original comes back byte for byte. File decryption is strict by design, so most failures come down to two causes.
Wrong Password During Decryption
A wrong password derives a different key, and AES-GCM reports an error instead of handing you garbage. Check capitalization, keyboard layout, and any trailing space; the matching decryptor only works with the exact original. There is no reset button, because the password is never stored. If it is lost, the encrypted file cannot be recovered.
The Encrypted File Was Modified
The authentication tag checks integrity, so changing even one byte of the .enc file makes decryption fail. Tampering is the point of that check, but accidents trigger it too: renaming the extension is harmless, while editing, compressing, or re-saving the file in another program is not. Fix it by going back to the untouched copy and decrypting that.
Encrypting Files with a Browser Encryptor Before Emailing a Payroll Export
On a Thursday afternoon, Priya, a freelance bookkeeper, has to send a client's payroll-export-march.xlsx to an accountant who uses a different email provider. The spreadsheet holds names, tax IDs, and salaries, so a plain attachment is out and Priya reaches for a browser-based file encrypter decrypter. The file is 1,962,340 bytes, and the accountant already has a phone number for a quick call, which makes a shared password realistic.
Priya opens the encryption page, drops the spreadsheet onto the upload area, and enters a four-word passphrase picked with dice from the EFF word list of 7,776 words. Then comes a click on Encrypt. The page returns payroll-export-march.xlsx.enc at 1,962,384 bytes, exactly 44 bytes larger, which matches the salt, IV, and authentication tag the tool stores with the ciphertext.
Before sending, Priya checks the strength of that choice against the tool's PBKDF2 setting. Four words from a 7,776-word list give 7,7764, or about 3.66 quadrillion combinations, so at 16,667 guesses per second an attacker needs an average of roughly 3,478 years to land on the passphrase protecting the .enc file.
The decision that follows is specific. Priya emails the .enc file, then phones the accountant with the passphrase instead of typing it into the same thread. As a final test, Priya runs the .enc file back through the decrypt tab on a second laptop, and the decryption side of the tool restores the spreadsheet with all rows intact. Had the check failed, the next step would have been re-encrypting from the original, never editing the .enc file, since one changed byte breaks the authentication tag.
File Encryption Tool Features and Security
A trustworthy tool for file encryption and decryption should explain exactly what happens to your data, and it should protect it by default. Here is what this one does:
- AES-256 encryption, a 256-bit key size that is considered secure against brute-force attacks and is the core of modern cryptography for files.
- Password-based encryption with PBKDF2, so you skip manual key management and never handle a random key file. Command-line programs sometimes offer automatic key generation instead.
- Authenticated encryption that detects any modification to the output.
- In-memory processing, so nothing is written to storage and no server or cloud copy exists.
- Instant download of the encrypted output as soon as the work finishes, with a simple progress indicator for bigger files.
In-Memory Processing and the Web Crypto API
The tool relies on the native Web Crypto API built into modern browsers such as Chrome, Firefox, Edge, and Opera. Because the work stays local, your file never travels over the network, which keeps the process safe, protects your privacy and keeps sensitive content out of anyone else's logs. Once the page has loaded it can even work offline, and a browser extension is a common way to get that behavior permanently. Security is strongest when the algorithm is a public standard such as the ones recommended by NIST and OWASP, not a homemade cipher. Open-source projects often publish the code under the MIT license so anyone can inspect it, and a secure design never depends on hidden steps.
AES vs RSA vs PGP for File Encryption
These three names come up in every conversation about file encryption, but they solve different problems. This comparison shows where each one fits:
| Feature | AES | RSA | PGP |
|---|---|---|---|
| Handles large files | Yes | No | Yes |
| Password-based | Yes | No | Optional |
| Multiple recipients | No | No | Yes |
| Key type | Shared secret | Public and private pair | Both |
Symmetric Encryption vs Asymmetric Encryption
AES is symmetric, so one secret protects the data and you only need to share that secret safely. Asymmetric encryption such as RSA uses a public and a private key, which makes public-key encryption ideal for key exchange but slow for big payloads. PGP combines both: it encrypts the file with a fast symmetric key, then wraps that key for each recipient, which is why it suits file sharing with multiple recipients. For a personal archive or an email attachment, AES with a strong password is simpler.
Password Strength for Encryption and Decryption
When you encrypt a file with this tool, the password is the only thing standing between an attacker and the .enc file, because the algorithm is rarely the weak point. AES-256 is computationally infeasible to break directly, so an attacker goes after the password instead, under the tool's 600,000-iteration PBKDF2 setting. The search space grows with every character, and halving it gives the average time to find a match:
$$T = \frac{62^{12}}{2 \times 16{,}667\ \text{guesses per second}}$$
For the 12-character password mapleRidge42, which draws from 62 letters and digits, that works out to about 3.1 billion years on average. An 8-character lowercase password drops to roughly 73 days under the same assumptions, which shows how fast weak choices fail.
Choosing a Strong Password
Length matters more than symbols. Use at least 12 characters, avoid dictionary words on their own, and never reuse a password from another account. A random passphrase works as well as a random string and is easier to type correctly when you decrypt files months later. The same habit helps when encrypting files in bulk, and it makes encrypt and decrypt files workflows repeatable. A password manager can hold it, though a backups habit matters too: keep the password and the encrypted copies in different places.
When Not to Use a File Encryptor
A password-based encryption tool is the right use case for single files, but it is the wrong choice in a few situations:
- Whole drives: tools such as VeraCrypt, BitLocker in Windows, and FileVault on a Mac handle disk-level encryption, including every one of your folders on the volume.
- Several readers: choose PGP when more than one person must open the file.
- Storing logins: use Argon2, bcrypt, or scrypt for hashing passwords, not this tool.
- Signatures: use RSA or ECC when you need to prove who sent something.
If a folder syncs to OneDrive, you can still encrypt files first so only ciphertext ever leaves your computer. Pair that with a recovery plan, because neither the tool nor anyone else can restore a forgotten password.
Frequently Asked Questions
- What file types can I encrypt?
- Any file at all -- documents, images, archives, videos -- since the tool operates on raw bytes rather than parsing the file's format. The encrypted output is a generic binary file (.enc) regardless of what you started with.
- How do I get my original file back?
- Switch to Decrypt mode, choose the .enc file, enter the exact same passphrase you encrypted it with, and click Decrypt File -- the original file downloads with its original name restored (the .enc suffix is stripped automatically).
- Why does the download start automatically?
- Both encryption and decryption produce a new file as the direct result, so this tool triggers a browser download immediately rather than displaying the (typically large, binary) result on the page -- the same behavior as any file-processing tool that hands you back a modified file.
- Is there a file size limit?
- The whole file is read into memory and encrypted in one pass, so very large files (many gigabytes) may be slow or hit your browser's memory limits -- this tool is best suited for typical document, image, and archive sizes rather than huge media files.
- Is my file uploaded anywhere?
- No. Encryption and decryption both happen entirely in your browser using the Web Crypto API -- the file is never uploaded, transmitted, or stored anywhere outside your own device.