Plagiarism detection API: submit text, poll the report.

Two endpoints, bearer auth, transparent credit pricing. Built for agencies, editorial pipelines and LMS-adjacent tools.

Your API key

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Endpoints

POST /api/v1/check/

Submit a text for checking. Returns 202 with a check_id. Body: JSON with a text field, optional deep boolean.

curl -X POST https://plagiarism.free/api/v1/check/ \
  -H "Authorization: Bearer YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{"text": "The text you want to check..."}'

GET /api/v1/check/<check_id>/

Poll for status; when status is done the full report is included: score, per-sentence match types with confidence and source excerpts, and the source list.

curl https://plagiarism.free/api/v1/check/CHECK_ID/ \
  -H "Authorization: Bearer YOUR_KEY"

Python example

import time
import requests

API = "https://plagiarism.free/api/v1/check/"
HEADERS = {"Authorization": "Bearer YOUR_KEY"}

r = requests.post(API, json={"text": open("essay.txt").read()}, headers=HEADERS)
check_id = r.json()["check_id"]

while True:
    report = requests.get(f"{API}{check_id}/", headers=HEADERS).json()
    if report["status"] in ("done", "failed"):
        break
    time.sleep(3)

print(report["score_pct"], "% matched")
for source in report["sources"]:
    print(source["pct_of_document"], source["url"])

JavaScript example

const API = "https://plagiarism.free/api/v1/check/";
const headers = { "Authorization": "Bearer YOUR_KEY", "Content-Type": "application/json" };

const { check_id } = await fetch(API, {
  method: "POST", headers, body: JSON.stringify({ text })
}).then(r => r.json());

let report;
do {
  await new Promise(res => setTimeout(res, 3000));
  report = await fetch(`${API}${check_id}/`, { headers }).then(r => r.json());
} while (!["done", "failed"].includes(report.status));

Pricing

Identical to the site: 1 credit = 1,000 words scanned, rounded up per check; deep checks cost double. Credit packs are valid 365 days; subscriptions refill monthly and include the API at every level. No separate API tier, no per-seat fees. See plans and packs

Checks run asynchronously (real, rate-limited web retrieval takes 20-45 seconds) - poll the status endpoint rather than holding the connection open. HTTP 402 means insufficient credits; the response includes what the check would cost.

Frequently asked questions

Two endpoints. POST /api/v1/check/ with your text returns a check_id; GET /api/v1/check/check_id/ returns status while the check runs and the full report JSON (score, matched sentences, sources) when done. Auth is a Bearer key from your account page. Code samples in curl, Python and JavaScript are below.

The same transparent unit as the site: 1 credit per 1,000 words scanned, rounded up per check. Credit packs start at $4.99 for 30 credits and are valid a full year; the $7.99/month Starter plan includes 60 credits and API access. No per-seat fees, no separate API pricing tier.

A check takes roughly 20-45 seconds because it performs real, rate-limited web retrieval and page comparison - the API is asynchronous for that reason. Submissions queue fairly; paid checks get priority. Poll the status endpoint every few seconds rather than holding the connection open.

Everything the web report shows: overall matched percentage, per-sentence match type (exact / near / none) with confidence, the matched source excerpt for each flagged sentence, and the source list with URLs and per-source match percentages. Enough to render your own report UI or gate a workflow.

Yes - that is what it is for: LMS-adjacent tools, editorial workflows, agency content pipelines. Volume is metered purely by credits, and the per-check word cap is 25000 words. If you need sustained high volume, contact us and we will provision for it rather than let queues degrade.