Base62 (0-9, a-z, A-Z) is URL-safe without percent-encoding and gives a wider keyspace than base36 — 62^7 is over 3.5 trillion 7-character keys.

How long should my keys be?

For a hobby shortener 6 characters is fine. At Bitly scale 7-8 is more comfortable to avoid collisions and to leave room for growth.

Are these collision-free?

Random keys are collision-resistant, not collision-free. Track issued keys in your database and retry on the rare conflict.

base62 · url-safe · short · local

Generate short URL keys

Q: Is generation local?

Yes. Bytes come from crypto.getRandomValues in your browser; nothing is sent to a server.

URL-safe base62 random keys for link shorteners, share codes, or invite tokens. Pick a length, see the key space, and grab a batch from cryptographic randomness.

Short URL Key Generator

Length

chars

Key space

3.52e+12

62^7

Generated

10 requested

Output

0 B

txt

input · controls

Base62 alphabet: A-Z, a-z, 0-9 — URL-safe without escaping.

Key space: 3.52e+12 distinct keys.

Collision risk at N keys is roughly N² / (2·62^length). Length 7 hits 1% collision around 80M keys.

output · keys (0)

Click Generate to mint keys

Quick Start

How short URL keys work

Base62 fits more entropy per character than base16. A 7-char base62 key has ~3.5 trillion possibilities — enough for a small shortener.

01
Pick a length
6 for very compact, 10-12 if you expect millions of keys.
Inputs are treated as UTF-8 throughout the pipeline and validated client-side as you type — nothing dispatches until the value is well-formed.
lengthinpututf-8client-sidevalidated
length · text7 · set
```
62^7 ≈ 3.5T
```
loaded · parsedclient-side
02
Choose count
Generate up to 500 keys per batch.
Each toggle re-computes through a memoised hook, so flipping options never resets your input and the UI stays snappy on large inputs.
countoptionslivememoisedtoggles
count · memoised10 · live
```
10 fresh keys
```
options set · memoisedlive
03
Generate
Crypto random bytes map to base62 characters with bias-acceptable modulo.
Randomness — where used — comes from crypto.getRandomValues, never Math.random. Heavy work sits in useMemo.
mintcomputeinstantlocaldeterministic
mint · instantbase62 · computed
```
fK2xZ9q
```
computed · instantinstant
04
Copy or download
Pipe into your shortener's reservation table.
Copy writes through navigator.clipboard and downloads use a Blob — zero network traffic. Same input plus same options always yield the same bytes.
exportcopydownloadzero-networkreproducible
ok · copiedready · copied
```
Copied
```
shipped · ready to shipsuccess

Pro tips

Pro tips for everyday utilities

Reach for crypto.getRandomValues

Cryptographically random for IDs, tokens, salts. Math.random is for animation and games, not security.

Sort IDs lexicographically

UUID v4 has no time ordering. Use ULID or UUID v7 if you need sorted IDs.

Mock data with seeds

Faker-style libraries can be seeded so tests are reproducible. Embed the seed in the fixture file.

Reference cards beat memory

Cheatsheets for Vim, Git, Docker, Linux signals are faster than man pages when you’re mid-flow.

Browser APIs vary

Touch events, gamepads, and clipboard differ across vendors. Feature-detect before use.

Persist in the right place

localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data.

Use Cases

When to use short keys

Shorteners, share codes, invites, tokens.

Link shorteners

Compact slugs that fit in tweets and DMs. Random values come from crypto.getRandomValues — cryptographically secure for tokens, salts, and session IDs. Math.random is deterministic enough for animations but predictable enough to be a security bug.

CSPRNG-backed

Share codes

Time-bound document sharing URLs. Pair with hashids, ULID, or UUID v7 when you need both random and sortable — useful for primary keys, public-facing IDs, and event log ordering without a sequence column.

reproducible

Invite tokens

One-shot codes for onboarding flows. Output is deterministic given the same seed, so fixtures and tests stay reproducible across CI runs and contributor machines. Embed the seed in the fixture file for full replay.

snappy

Magic links

Opaque tokens in passwordless email login. Heavy work runs through useMemo so the UI stays snappy on large inputs. Same input + same options yields identical bytes — the kind of stability snapshot tests rely on.

feature-detected

Coupon codes

Sub-10 character codes that scan well. Storage tools persist to the right backend: localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data. Pick the right shelf and quota worries disappear.

deterministic

Print QR payloads

Shorter payloads → smaller QR codes. Browser feature detection: clipboard, fullscreen, gamepad, and Web Bluetooth APIs gracefully fall back when unavailable. No surprise white screens on Safari or older Firefox.

production-ready

FAQ

Frequently asked questions

Is mod 62 biased?

Slightly — but only the first 8 of 256 bytes are over-represented. Negligible for shortener use; switch to rejection sampling for cryptographic keys.

Are these unique?

Statistically yes, but the system DB must enforce a unique constraint and retry on collision.

Why base62 over base64?

Base64 includes + / = which require URL escaping. Base62 (A-Z a-z 0-9) is safe everywhere.

Can I exclude ambiguous chars?

Not here. For 0/O/I/l-free output, use the Custom Alphabet ID Generator.

Does it run locally?

Yes — keys are minted via crypto.getRandomValues in your browser. Nothing is sent to a server.

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