How do I calculate the bcrypt hash of a file?

Click the upload area or drag and drop your file onto the page. The tool will read the file content, process it through the bcrypt algorithm with a configurable cost factor (default 10), and display the resulting 60-character bcrypt hash in the format $2a$[cost]$[22 char salt][31 char hash]. The hash is computed by treating the file content as binary data and running it through bcrypt's Blowfish-based key derivation function with automatic salt generation. You can then copy the hash to your clipboard for verification or storage purposes. The hashing happens entirely in your browser using JavaScript—your file is never uploaded to any server, ensuring complete privacy. For large files, bcrypt hashing may take longer than fast algorithms like SHA-256 because bcrypt is intentionally slow for security. The tool shows file details including name, type, size, and the resulting bcrypt hash with embedded salt and cost factor. For images, you will see a preview before hashing to verify you have selected the correct file. Bcrypt produces a 60-character output that includes the algorithm version, cost factor, salt, and hash—everything needed for verification in a single string.

What file types can I calculate bcrypt hashes for?

You can calculate bcrypt hashes for absolutely any file type—images (JPG, PNG, GIF, WebP, SVG, BMP), documents (PDF, DOC, DOCX, TXT, CSV, MD), archives (ZIP, RAR, TAR, GZ), audio files (MP3, WAV, FLAC, OGG), video files (MP4, AVI, MOV, MKV), executables, databases, fonts, code files, configuration files, and more. Bcrypt processes raw binary file content through its Blowfish-based key derivation function, producing a password-style hash regardless of file format. The hash is calculated from the file content at the binary level, not the filename or metadata, so renaming a file does not change its hash. This makes bcrypt suitable for password-based file protection where you want to verify a file using a passphrase-derived key, creating unique file identifiers with password-like security properties, key derivation from file content for encryption applications, and generating checksums that require computational effort to verify. Unlike fast hash functions like SHA-256 that are optimized for speed, bcrypt is intentionally slow with adjustable computational cost, making it better suited for scenarios where you want rate-limiting or protection against rapid brute-force verification attempts. Bcrypt includes automatic salt generation, so each file hash contains a unique random salt embedded in the output.

Why use bcrypt for file hashing instead of SHA-256 or other algorithms?

Bcrypt is designed for password hashing and password-based key derivation, not general-purpose file hashing. For most file verification use cases (checking downloads, detecting duplicates, ensuring integrity), fast algorithms like SHA-256, SHA-512, or BLAKE2 are better choices because they are optimized for speed and can process large files quickly. However, bcrypt is useful for specific scenarios where you want intentional slowness and computational cost. Use bcrypt for files when you need password-based key derivation from file content, rate-limiting on verification attempts to prevent brute-force attacks, key stretching for encryption key generation from file data, or proof-of-work systems requiring computational effort. Bcrypt's adaptive cost factor allows you to control how slow the hashing is—higher cost factors make attacks more expensive. The algorithm uses the Blowfish cipher in an expensive key setup phase with salt and key stretching, producing output that includes the cost factor, salt, and hash in a single 60-character string. This embedded metadata makes bcrypt hashes self-describing. For regular file checksums, download verification, or duplicate detection, use SHA-256 instead—it is much faster (gigabytes per second vs. kilobytes per second with bcrypt) and more appropriate for integrity checking. Bcrypt's 72-byte maximum input length means large files must be chunked or pre-hashed, adding complexity. Choose bcrypt when you specifically need password-style security properties; otherwise, use SHA-256 or BLAKE3 for file hashing.

Is there a file size limit for bcrypt hashing?

There is no hard file size limit imposed by the tool, but practical considerations apply. Bcrypt has a maximum input length of 72 bytes, so files larger than 72 bytes must be chunked or pre-processed (typically by hashing the file with a fast algorithm like SHA-256 first, then bcrypt-hashing that digest). Most implementations handle this automatically. Browser memory limitations also apply—most modern browsers can process files up to 100-500 MB without issues, though bcrypt's computational cost makes large file hashing slow. For example, with cost factor 10, bcrypt processes approximately 4-8 KB per second (compared to 500+ MB per second for SHA-256), so a 10 MB file could take 20-40 minutes to hash directly. To handle large files efficiently, implementations typically read the file in chunks, hash each chunk with a fast algorithm, concatenate the digests, then apply bcrypt to the final result. The tool processes files entirely in browser memory for security and privacy, so available RAM determines the maximum practical file size. The resulting bcrypt hash is always exactly 60 characters regardless of input file size. For very large files (over 1 GB), consider using command-line tools or fast hash functions like SHA-256, SHA-512, or BLAKE3 instead, reserving bcrypt for password hashing and key derivation scenarios where intentional slowness is desired.

What is the cost factor for file bcrypt hashing?

The cost factor (work factor) controls how computationally expensive bcrypt hashing is, ranging from 4 to 31. Each increment doubles the time required. For file hashing, the cost factor determines how long it takes to compute the hash and how difficult it is for attackers to brute-force verify files. Cost factor 10 (default) takes approximately 100-200 milliseconds to hash 72 bytes on modern hardware, making it suitable for password verification but slow for large files. Cost factor 12 takes around 400-800 milliseconds, providing higher security against brute-force attacks. Cost factor 14 or higher is used for maximum security but significantly impacts performance. When choosing a cost factor for files, consider your use case. For password-based file encryption where you derive keys from passphrases, higher cost factors (12-14) provide better security against dictionary attacks on the passphrase. For file integrity verification where speed matters, lower cost factors (8-10) or switching to SHA-256 may be more appropriate. For proof-of-work systems where you want to prove computational effort was spent, adjust the cost factor based on desired difficulty. As computers get faster, you can increase the cost factor over time to maintain security. This tool uses cost factor 10 by default, balancing security and performance. Remember that bcrypt's slowness is intentional—it protects against rapid brute-force attacks by making each verification expensive. Test performance with your file sizes and hardware to choose an appropriate cost factor.

How do I verify files using bcrypt checksums?

To verify a file using bcrypt, you need both the original bcrypt hash and the file you want to verify. Upload the file to this tool with the same cost factor used for the original hash (the cost factor is embedded in the hash string after $2a$), then compare the calculated hash with the original. If the hashes match exactly (all 60 characters identical including the salt portion), the files are identical at the binary level. If even one character differs, the files are different or the file has been modified. However, bcrypt verification differs from regular hash verification because bcrypt includes a random salt—the same file will produce different bcrypt hashes each time you hash it with different salts. To properly verify files with bcrypt, you must use the same salt from the original hash. Most bcrypt implementations extract the salt from the stored hash automatically during verification. For file verification, it is generally better to use deterministic hash functions like SHA-256 where the same file always produces the same hash, making verification straightforward. Bcrypt is more suited for password verification where the salt is managed automatically by bcrypt libraries. If you are using bcrypt for file-based key derivation, store the full 60-character hash (which includes the salt and cost factor) and use bcrypt's verify function rather than comparing hashes manually. For simple file integrity checking and duplicate detection, SHA-256, SHA-512, or BLAKE3 are more appropriate and efficient choices.

Can identical files have different bcrypt hashes?

Yes! This is a key difference between bcrypt and deterministic hash functions like SHA-256. Bcrypt automatically generates a new random 128-bit salt for each hash operation, so the same file hashed twice with bcrypt will produce two completely different 60-character hash strings, even though the salt is embedded in the hash output. This is intentional for password hashing—if two users have the same password, their bcrypt hashes should be different to prevent rainbow table attacks. However, for file verification and duplicate detection, this behavior is problematic because you cannot simply compare bcrypt hashes to check if files are identical. If you hash the same file twice, you will get different results due to different salts. To verify a file against a bcrypt hash, you must use bcrypt's verify function which extracts the salt from the stored hash, rehashes the file with that same salt, and compares the results. This is how bcrypt password verification works. For file-based applications, this means you must store the full 60-character bcrypt hash (not just generate and compare hashes). If you need deterministic hashes where the same file always produces the same hash (for deduplication, caching, or simple verification), use SHA-256, SHA-512, BLAKE2, or BLAKE3 instead. Bcrypt is designed for password protection and key derivation where salt randomization is a security feature. For file integrity where deterministic output is needed, choose a cryptographic hash function designed for that purpose.

Can I calculate bcrypt hashes for images and see previews?

Yes! Upload any image file (JPG, PNG, GIF, WebP, BMP, TIFF, SVG, ICO) and the tool will show a preview of the image before calculating its bcrypt hash. The hash is computed from the binary image data at the byte level, not the visual appearance—visually identical images with different compression, metadata, color profiles, or formats will have different hashes. This is useful for password-based image protection where you derive encryption keys from image content, generating unique identifiers for images that require computational effort to verify, creating rate-limited verification systems for image-based secrets, or proof-of-work systems using image data. After hashing, you get a 60-character bcrypt output that includes the algorithm version ($2a$), cost factor (default 10), random salt (22 characters), and hash (31 characters). Remember that even minor changes to the image file (editing metadata, changing compression, rotating, or cropping) will produce completely different hashes due to bcrypt's avalanche effect. Also note that bcrypt generates a new random salt each time, so hashing the same image twice produces different outputs. For comparing images byte-for-byte or detecting duplicate photos, use deterministic hash functions like SHA-256 instead. For perceptual similarity (finding visually similar images regardless of format or edits), use perceptual hashing algorithms like pHash or dHash. Bcrypt is most appropriate when you need password-style security properties for image-derived keys.

Is my file safe when using this bcrypt calculator?

Yes, absolutely safe! All bcrypt hashing happens entirely in your browser using JavaScript. Your file is never uploaded to any server, never transmitted over the internet, and never stored anywhere except temporarily in your browser memory during the hashing process. Once you close or refresh the page, all data is immediately cleared from memory. This client-side approach ensures complete privacy—even the most sensitive files (confidential documents, private photos, encryption keys, proprietary data, classified information) can be safely hashed without leaving your device. Bcrypt is a one-way hash function, meaning you cannot reverse the hash to recover the original file—the 60-character output is just a cryptographic fingerprint that includes salt, cost factor, and hash data. However, if someone has both your file and your bcrypt hash, they can verify the file matches (using bcrypt's verify function), so treat bcrypt hashes of sensitive files with appropriate care. The hash itself does not reveal file content and cannot be used to reconstruct the file. The tool operates entirely offline after loading—you can disconnect from the internet and it will continue working. Always use HTTPS-secured websites (like this one) to prevent man-in-the-middle attacks when loading the tool. For production systems with maximum security requirements, consider using offline command-line bcrypt tools or verify the JavaScript source code is truly client-side. Bcrypt's 20+ year track record and use by millions of systems makes it one of the most trusted password-based key derivation functions available.

What are common use cases for bcrypt file hashing?

Bcrypt file hashing is used in specialized scenarios where password-style security properties are needed for files, rather than general-purpose file verification. Common use cases include password-based key derivation where you generate encryption keys from file content (the file acts as the password), requiring computational effort before the key can be derived for encryption or decryption. License key validation systems use bcrypt to rate-limit verification attempts, making it expensive for attackers to brute-force valid keys. Proof-of-work systems where users must prove they performed computational work on a file before submission. File-based authentication where possession of a specific file (key file) is required and verification is intentionally slow to prevent rapid testing of stolen files. Blockchain and cryptocurrency applications using file content to derive wallet keys with adaptive cost factors. Time-locked encryption where files can only be decrypted after spending a certain amount of computational effort. Digital rights management (DRM) systems where file hashing must be slow to prevent rapid cracking. However, for most file-related tasks, bcrypt is not the optimal choice. Use SHA-256, SHA-512, or BLAKE3 for file integrity verification, download checksums, duplicate detection, and content-addressable storage. Use Argon2 for password-based key derivation in new systems. Use HMAC-SHA256 for authenticated file verification with shared secrets. Bcrypt remains valuable for legacy systems already using it and specific scenarios requiring intentional computational slowness with adaptive cost. The algorithm's 20+ year track record and widespread library support make it reliable for password-based file protection.