Generate an RFC 4226 counter-based HMAC one-time password from a base32 secret a
Generate an RFC 4226 counter-based HMAC one-time password from a base32 secret and counter. Configurable digits (6–10, default 6) and algorithm (SHA1/SHA256/SHA512, default SHA1). An invalid base32 secret is a clean 400.
Answeringour last check, 2026-09-24
1 of 1checks answered this week
453 msmedian answer time
$0.004listed price per call
$0.004price it asked us
Paid test badge: not yet. The checks above are free: we call the tool without paying and read the payment request it sends back. The Verified badge needs paid calls whose answers match the promised output, and nobody can buy a badge.
Endpoint
POST https://otp.openverbs.com/v1/hotp
| Category | Everything else |
|---|---|
| Provider host | otp.openverbs.com |
| Networks | eip155:8453 |
| Payment schemes | exact |
| Self-reported calls, 30 days | 3 from 1 payers (the provider's figure, not ours) |
Our checks, last 30 days
| Day | Result | HTTP | Asked | Time |
|---|---|---|---|---|
| 2026-09-24 | valid payment request | 402 | $0.004 | 453 ms |
Example input (from the provider)
{
"body": {
"algorithm": "SHA1",
"counter": 1,
"digits": 6,
"secret": "example"
},
"bodyType": "json",
"method": "POST",
"type": "http"
}
Promised output schema (from the provider)
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"properties": {
"input": {
"additionalProperties": false,
"properties": {
"body": {
"additionalProperties": false,
"properties": {
"algorithm": {
"description": "HMAC algorithm. Default SHA1.",
"enum": [
"SHA1",
"SHA256",
"SHA512"
],
"type": "string"
},
"counter": {
"description": "The HOTP counter value.",
"minimum": 0,
"type": "integer"
},
"digits": {
"description": "Number of code digits. Default 6.",
"maximum": 10,
"minimum": 6,
"type": "integer"
},
"secret": {
"description": "Base32-encoded shared secret.",
"maxLength": 1024,
"minLength": 1,
"type": "string"
}
},
"required": [
"secret",
"counter"
],
"type": "object"
},
"bodyType": {
"enum": [
"json",
"form-data",
"text"
],
"type": "string"
},
"method": {
"enum": [
"POST"
],
"type": "string"
},
"type": {
"const": "http",
"type": "string"
}
},
"required": [
"type",
"method",
"bodyType",
"body"
],
"type": "object"
}
},
"required": [
"input"
],
"type": "object"
}