With doc.cheap’s passport OCR API, a Node.js server can send a Base64-encoded image to POST https://api.doc.cheap/v1/scans and receive structured scan JSON in the same request. The integration has three separate decisions to get right: check HTTP success, interpret the OCR result in meta.status, and save meta.billed with the scan record. For safe retries after timeouts, reuse the same idempotency key and identical request body for the same logical scan.
The endpoint, statuses, billing behavior, and limits below describe doc.cheap’s service, not a universal OCR standard. The provider’s tutorial by Teoh Chin Heng was published September 24, 2026, and updated September 26, 2026; check its current API documentation before deployment.
What the Node.js request sends and returns
The tutorial targets Node.js 18 or later, which includes built-in fetch. It reads an image file, encodes its bytes as Base64, and sends a JSON request to doc.cheap’s scan endpoint. The API responds synchronously with structured JSON rather than requiring a separate job-polling flow, according to the doc.cheap tutorial and API documentation.
Keep the API key on your server; do not expose it in browser code. The essential implementation pattern is to serialize the payload once and retain that exact serialized body for any retry:
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import { readFile } from 'node:fs/promises';
import { randomUUID } from 'node:crypto';
const image = await readFile('./passport.jpg');
const payload = {
image: image.toString('base64'),
// Include only the options required by your integration.
};
const body = JSON.stringify(payload);
const idempotencyKey = randomUUID();
const response = await fetch('https://api.doc.cheap/v1/scans', {
method: 'POST',
headers: {
'Authorization': `Bearer ${process.env.DOC_CHEAP_API_KEY}`,
'Content-Type': 'application/json',
'Idempotency-Key': idempotencyKey,
},
body,
});
const result = await response.json();
if (!response.ok) {
throw new Error(`Scan request failed: ${result.error?.code ?? response.status}`);
}
// HTTP success is not the same as successful text recognition.
console.log(result.meta.status, result.meta.billed);This is a request-shape illustration; use the current documentation for the exact authentication header, payload fields, response schema, and supported options. In production code, also handle a response that is not valid JSON rather than assuming every error response has a parseable body.
Check HTTP success separately from the OCR outcome
Node’s fetch does not reject merely because the server returned an HTTP 4xx or 5xx response. Parse the response where possible and inspect response.ok for transport/API success. Only after that check should your application branch on meta.status, which describes what recognition did with the submitted image. A blurry or unsupported image can still receive HTTP 200.
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| Successful-HTTP status | Meaning and application response |
|---|---|
recognized |
Recognition returned document data. Store and validate the fields your application needs. |
no_document_found |
The image did not yield a detected document. Ask for a better-framed image rather than blindly resending the same one. |
unreadable |
The image could not be read clearly. Request better lighting, focus, or camera angle. |
unsupported_document |
The submitted document type is unsupported. Do not retry the same input expecting a different result. |
rejected |
The tutorial describes this as a service-side rejection that may merit one retry; avoid an unlimited retry loop. |
For non-2xx responses, inspect the documented error code and correct the cause. Input, size, authentication, and credit errors are not transient failures and should not be retried unchanged. See doc.cheap’s error-handling guidance for its provider-specific semantics.
Retry a timed-out scan without creating a second logical request
A timeout is ambiguous: the client may not know whether the service processed the request before the connection failed. Generate one idempotency key per logical scan, then reuse that key and byte-for-byte identical JSON body when retrying that scan. A new key means a new logical request; changing the body while keeping the old key is not a safe way to revise a submission.
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- Use a stable application identifier for the scan record and associate it with the idempotency key.
- Construct the request body once; do not rebuild it from mutable state for a retry.
- Retry only selected transient failures, with a timeout and bounded retry policy.
- Do not loop on authentication, invalid-input, size, or credit errors.
According to the tutorial, reusing a key with a different body returns 409 idempotency_conflict. It also describes a retention edge case: with retain_hours: 0, replay is unavailable for 24 hours, after which reuse may result in a new scan. Idempotency guarantees and retention are provider-specific, so verify the current contract before relying on a key for billing protection.
Persist the billed flag with the scan
meta.billed is a per-response field. Store it alongside the scan result and your own request identifier so reporting can distinguish responses the provider marks billable from those it does not. Do not infer cost solely from HTTP status or from whether OCR recognized the document.
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Sandbox behavior needs separate treatment: doc.cheap says its public sandbox is not charged, even though its billed value simulates whether the corresponding live request would be billed. Therefore billed: true in a sandbox response is not evidence that money was charged. Keep environment or mode with your record if sandbox and live results share a database.
Protect passport images and interpret OCR narrowly
A passport image is sensitive personal data. Do not log the image, Base64 payload, or full request body. The tutorial says uploads are held in memory rather than written to durable storage, while results may be retained; it also says processing occurs in the EU and describes configurable result retention. These are vendor-published statements, not an independent security audit. Confirm the provider’s current retention, data handling, and processing terms for your use case.
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The tutorial also identifies a return_portrait: false option for omitting a portrait crop when your application does not need it. Use the least data your workflow requires, and test with a synthetic specimen rather than a real passport where possible.
OCR extracts and structures information; it does not establish that the document is genuine or that the person presenting it is its rightful holder. The tutorial describes authenticity.overall as not_checked. Do not present an OCR result or MRZ check as forgery detection or identity verification.
Provider terms and an SDK alternative
All figures here are doc.cheap product terms as reported in its 2026 tutorial or documentation, not independent industry statistics. Their availability and applicability can change:
| Term | doc.cheap figure and qualification |
|---|---|
| Public access | 10 free recognized documents per IP address in total, and up to 10 requests per hour, as reported in the tutorial published September 24, 2026, updated September 26, 2026. |
| Account allowance | 100 free documents each month, according to doc.cheap’s 2026 materials. |
| Live price | $0.01 per billed live document, according to doc.cheap’s 2026 materials. |
| Registered-key rate limit | 60 requests per minute, according to the tutorial’s 2026 account of the service. |
If you prefer an SDK, StructOCR documents a Node.js SDK with scanPassport() and Base64 conversion, as well as a JSON/Base64 REST API. That establishes an implementation alternative, not equivalent retry, billing, pricing, or retention behavior; its documentation does not provide a like-for-like comparison on those terms. See StructOCR documentation.
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