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API · /checksum-api

Checksum API

healthy 3,343 Subscribers

Fast non-cryptographic checksums as an API. Compute CRC-32 — the integrity check used by ZIP, gzip, PNG and Ethernet — and Adler-32 — the checksum used by zlib — over UTF-8 text, hex or base64 input, returned in hex and as signed and unsigned 32-bit integers. Ideal for file- and message-integrity verification, cache keys and ETags, change detection and deduplication, where you want a quick fingerprint rather than a secure hash. Pure local computation — no key, no third-party service, instant; send binary via the hex or base64 encoding (up to 4 MB). Live, nothing stored. 4 endpoints. Explicitly NOT for security — for cryptographic digests (MD5, SHA-256, HMAC) use a hashing API instead.

#checksum #crc32 #adler32 #integrity #hashing #developer-tools
api.oanor.com/checksum-api
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Machine-readable spec so AI agents can integrate this API.

/api/checksum-api/openapi.json
/api/checksum-api/llms.txt

Discovery: GET /api/index.json lists every API.

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
86 ms
Server probes · 24h
Subscribers
3,343
active
Total calls
52
last 7 days
status Full status page → · 24 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 700 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 700 calls/month
  • 2 req/sec
  • CRC-32 + Adler-32
  • No credit card
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Starter

€0.80 /month

  • 5,500 calls / month
  • 8 requests / second
  • Hard cap (429 above quota, no overage)
  • 5.5k calls/month
  • 8 req/sec
  • utf8 / hex / base64 input
  • Email support
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Pro

€18.40 /month

  • 122,000 calls / month
  • 20 requests / second
  • Hard cap (429 above quota, no overage)
  • 122k calls/month
  • 20 req/sec
  • Integrity / dedup pipelines
  • Priority support
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Mega

€54.40 /month

  • 630,000 calls / month
  • 50 requests / second
  • Hard cap (429 above quota, no overage)
  • 630k calls/month
  • 50 req/sec
  • Platform scale
  • Dedicated SLA
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Related APIs

Other APIs with overlapping tags.

Check Digit API

Add and verify check digits with the standard algorithms — Luhn (mod 10), Verhoeff, Damm and ISO 7064 mod 97-10 — on any number. The generate endpoint returns the check digit(s) and the complete number; the validate endpoint tells you whether a number's check digit is correct. Luhn is the familiar mod-10 scheme behind credit cards, IMEI and many ID numbers; Verhoeff and Damm are single-digit schemes that also catch all adjacent-transposition errors; mod 97-10 produces two check digits and is the scheme used by IBAN. Perfect for generating and validating reference, account, membership and order numbers, and for data-entry integrity. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 4 endpoints. Distinct from credit-card and barcode validators, which apply a fixed algorithm to one specific number format.

api.oanor.com/checkdigit-api

Birthday Paradox API

Birthday-paradox and collision-probability maths as an API, computed locally and deterministically. The probability endpoint computes the chance that at least two of n people share a birthday among d equally likely days, P = 1 − Π(1 − i/d), evaluated in log space for accuracy — the famous result that just 23 people give about a 50.7 % chance, 50 people about 97 % and 70 people about 99.9 %. The people-needed endpoint inverts it: the smallest group size to reach a target probability (23 for 50 %, 57 for 99 %), with the √(2·d·ln(1/(1−p))) approximation. The collision endpoint generalises the birthday bound to any space — pass a number of buckets or a hash size in bits — and returns the collision probability P ≈ 1 − e^(−n²/2d), the rule behind hash collisions and UUID-uniqueness estimates, where a 50 % chance needs roughly 1.177·√d items. Days and buckets default to 365. Everything is computed locally and deterministically, so it is instant and private. Ideal for probability-education, security, cryptography, hashing, data-engineering and statistics app developers, collision-risk and birthday-problem tools, and teaching material. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is the birthday/collision probability; for full distributions use a probability API.

api.oanor.com/birthdayparadox-api

A/B Bucketing API

Deterministic A/B testing and feature-flag assignment — no database, no stored state. The bucket endpoint hashes a key (a user id, session or device) into a stable bucket from 0 to N-1 that never changes for that key, and can decide whether the key is inside a percentage rollout; because the decision is monotonic, raising the percentage only ever adds users, so a gradual ramp-up is sticky and no one flips back out. The variant endpoint assigns one of several weighted variants — a simple control/treatment split or any multivariate test — consistently for the same key, honouring custom weights. Mixing in an experiment name keeps independent experiments independent, and because the same inputs always produce the same answer, your client and server (and any edge function) agree on the assignment without any coordination or lookups. Hashing is FNV-1a with an avalanche mix, giving uniform, stable buckets across languages and machines. It runs entirely locally, so it is instant, deterministic and private. Ideal for feature flags and gradual rollouts, A/B and multivariate experiments, canary releases, holdouts and kill-switches, and consistent UI bucketing across web and mobile. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This assigns experiments deterministically; to test whether a result is statistically significant use a statistics API.

api.oanor.com/abtest-api

Balloon Decor API

Party-balloon maths as an API, computed locally and deterministically — the helium-lift and balloon-count numbers a party planner or balloon artist decorates by. The helium endpoint gives a balloon’s lift from its inflated diameter: net lift is the inflated volume times the difference between air and helium density, about 1.046 grams per litre, so a fully inflated 11-inch latex balloon (around 11.4 litres) lifts roughly 12 grams gross and about 9 after its own weight, while a 36-inch giant lifts hundreds of grams. The float endpoint flips it around — how many balloons to float a payload = the weight divided by the net lift per balloon, rounded up, so a 50-gram card floats on six 11-inch balloons. The garland endpoint sizes an organic balloon garland or arch from its length: about 12 balloons per foot in a mix of sizes — roughly 40 % 5-inch, 45 % 11-inch and 15 % 16-inch for that full, textured look — so a 10-foot garland takes about 120 balloons, denser if you want it lush. Everything is computed locally and deterministically, so it is instant and private. Ideal for party-planning, event-decor, balloon-artist and celebration app developers, decor-estimator and shopping-list tools, and event software. Pure local computation — no key, no third-party service, instant. Inches and grams. Live, nothing stored. 3 compute endpoints.

api.oanor.com/balloon-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Checksum API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Checksum API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Checksum API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Checksum API cost?
Checksum API has a free tier with 100 calls / month. Paid plans start at €0.80 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Checksum API GDPR-compliant?
All requests to Checksum API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/checksum-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/checksum-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/checksum-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/checksum-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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