⌘ K
base91 · 91 printable ASCII · encode · live

Encode & decode Base91

basE91 squeezes binary into 91 printable ASCII chars — about 23% denser than Base64 while staying email and JSON safe.

Base91 Converter
Input
43 B
1 lines
Output
53 B
1 lines
Status
ready
live
Ratio
1.23×
out/in
input · text
output · base91
nX^Iz?T1s!2t:aRn#o>vf>6C9#`##mlLK#_1:Wzv;RG!,a%q3Lc=Z
Quick Start

How to convert Base91

basE91 packs 13 or 14 bits per character pair using a 91-glyph printable set. Output is shorter than Base64 but stays free of -, \, and quotes.

  1. 01

    Pick mode

    Encode bytes to basE91, or decode basE91 to bytes.

    Bytes flow through TextEncoder/TextDecoder for predictable UTF-8 semantics — emoji, surrogate pairs, and combining marks all encode losslessly.

    modeUTF-8TextEncoderlosslesslive
    mode · raw bytesencode · UTF-8
    encode · decode
    loaded · UTF-8MIME · ready
  2. 02

    Paste payload

    UTF-8 in encode mode; basE91 string in decode. Stray whitespace is ignored.

    Hash and signature operations call crypto.subtle from the Web Crypto API, so output matches OpenSSL / Node bit-for-bit.

    utf8Web Cryptosubtledeterministiclive
    input · optionstext · live
    The quick brown fox…
    options applied · livelive
  3. 03

    Live convert

    Two output chars represent up to 14 bits of input — efficient packing.

    Options re-run instantly through useEffect + useMemo — switching URL-safe mode or padding doesn’t re-encode from scratch.

    livememoisedoptionsinstantreactive
    out · encodedb91 · ready
    >OwJh>}AQ
    encoded · livelossless
  4. 04

    Copy or download

    Drop straight into a JSON string or HTTP body.

    Copy uses the Async Clipboard API; downloads ship via Blob with the appropriate MIME (text/plain, image/png, …) so external tools recognise them.

    exportclipboardblobMIME-correctclient-side
    ✓ · copiedready · done
    ✓ Copied
    shipped · ready to shipsuccess
Pro tips

Encoding without surprises

Always UTF-8 first

Use TextEncoder / TextDecoder for bytes ↔ string conversion. btoa alone breaks on non-ASCII.

URL-safe vs standard Base64

Standard uses +, /, =; URL-safe swaps to -, _, no padding. Don’t mix them.

Hashes aren’t passwords

SHA-256 is fast; that’s good for fingerprints, bad for passwords. Use bcrypt / argon2 for credentials.

Watch padding rules

Some decoders are strict about = padding, others auto-pad. If round-trips fail at exactly 1 or 2 bytes, check padding.

Use Web Crypto for keys

Generate cryptographic keys via crypto.subtle, never Math.random. The latter is predictable.

JWT decode ≠ verify

Decoding a JWT just splits and base64-decodes. Verification needs the issuer’s public key / shared secret.

Related toolsBase85 ConverterBase64 EncoderBase62 ConverterBase58 ConverterBase32 ConverterText to Hex
Use Cases

When to use Base91

Dense embedding, JSON-safe binaries, low-bandwidth.

JSON binary fields

Tighter than Base64 inside JSON strings — quotes still safe. Output round-trips losslessly with the matching decoder — both run client-side, so end-to-end testing happens in a single tab. Encoding flows through TextEncoder for predictable UTF-8 semantics.

RFC-compliant

Embedded firmware

Squeeze updates into smaller OTA payloads. Web Crypto's subtle.digest produces output that matches OpenSSL, GPG, and Node's crypto module byte-for-byte. That makes the result trustworthy as a content fingerprint, ETag, or integrity check.

OpenSSL-matched

Bandwidth-bound feeds

Telemetry over LoRa, SMS, or slow links. Pairs cleanly with HMAC, JWT, and signed-URL workflows where bit-level correctness matters. The browser's crypto stack is FIPS 140-validated in Chrome and Firefox, so it's production-grade.

lossless

Storage compression

Pack blobs into text columns without binary types. Output uses canonical RFC 4648 / 7515 alphabets so curl, openssl, and any standards-compliant decoder accept it as input. URL-safe variants drop padding for tokens that travel in query strings.

byte-identical

Logs & traces

Stash structured binary diagnostics inside text logs. Heavy hashing runs through useMemo so large inputs don't block typing. PBKDF2, bcrypt, and Argon2 expose configurable cost factors — tune for your threat model, not the default.

spec-grade

Email attachments

Survives SMTP 7-bit transports just like Base64. Same input plus same options always yields identical bytes. That's the foundation for content-addressed storage (IPFS, Git, S3 ETags) and means the output is safe to commit to fixtures.

production-ready
FAQ

Frequently asked questions

basE91 hits ~22.97% overhead vs ASCII85's 25% — slightly tighter, and avoids `\` so it nests safely in JSON strings without escaping.
A-Z, a-z, 0-9, plus the printable specials (excluding -, \, and '). 91 glyphs total — the largest practical printable-ASCII set.
No — basE91 has a de-facto reference implementation by Joachim Henke but no RFC. Use the same library on both ends.
Unknown characters are skipped, so line wraps and stray whitespace decode fine.
No — encode and decode run locally in your browser.
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