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API · /ethsignatures-api

Ethereum Signatures API

healthy 4,300 Subscribers

Decode Ethereum smart-contract function and event signatures, keyless. Turn a 4-byte function selector (the first 4 bytes of any transaction calldata, e.g. 0xa9059cbb) into its human-readable function signature (transfer(address,uint256)), decode a 32-byte event topic from a log into its event signature, or search the database by name to find a selector. Many selectors have hash collisions — the API flags the original / canonical signature. Backed by the open 4byte.directory database, live. Essential for transaction decoders, block explorers, wallets, security tools and on-chain analytics — the signature-decoding layer for any EVM tooling.

#ethereum #signatures #4byte #evm #calldata #abi #crypto
api.oanor.com/ethsignatures-api
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Machine-readable spec so AI agents can integrate this API.

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

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

API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
273 ms
Server probes · 24h
Subscribers
4,300
active
Total calls
20
last 7 days
status Full status page → · 12 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 5,000 calls / month
  • 3 requests / second
  • Hard cap (429 above quota, no overage)
  • 5,000 calls/month
  • 3 req/sec
  • Function · event · search
  • No credit card
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Starter

€9.50 /month

  • 120,000 calls / month
  • 8 requests / second
  • Hard cap (429 above quota, no overage)
  • 120k calls/month
  • 8 req/sec
  • Canonical resolution
  • Email support
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Pro

€32.50 /month

  • 800,000 calls / month
  • 20 requests / second
  • Hard cap (429 above quota, no overage)
  • 800k calls/month
  • 20 req/sec
  • Bulk decoding
  • Priority support
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Business

€94.00 /month

  • 5,000,000 calls / month
  • 50 requests / second
  • Hard cap (429 above quota, no overage)
  • 5M calls/month
  • 50 req/sec
  • Commercial use
  • Dedicated SLA
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api.oanor.com/eipregistry-api

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api.oanor.com/compound-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Ethereum Signatures API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Ethereum Signatures API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Ethereum Signatures 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 Ethereum Signatures API cost?
Ethereum Signatures API has a free tier with 100 calls / month. Paid plans start at €9.50 / 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 Ethereum Signatures API GDPR-compliant?
All requests to Ethereum Signatures 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/ethsignatures-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/ethsignatures-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/ethsignatures-api/SOME_PATH");
curl_setopt($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/ethsignatures-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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