Overview

Noplag is a plagiarism checker for writers, publishers, and institutions that need to trace copied passages to their sources. Its strongest case is evidence-rich reporting across web and academic collections; it is a poor fit when paraphrase detection is essential.

The service pairs a hosted workflow with an engine released under Apache 2.0. Reports link each match to its source and show the similarity score and overlapping text, with PDF export—useful for reviewing a flag rather than relying on a score alone.

Key features

Matching and reports

Noplag accepts DOCX, PDF, TXT, ODT, and RTF files, pasted text, or a URL. Its live engine uses winnowing fingerprints and live-web matching to identify verbatim and near-verbatim overlap. Checks can draw on the open web, Common Crawl, Wikipedia, academic indexes, the Noplag Database, and users’ own folders. That breadth serves source tracing, but does not turn the result into a general measure of originality: the current engine does not detect paraphrase.

Detection is calibrated for English, Spanish, Portuguese, Polish, and Ukrainian. MinHash LSH and vector reranking are future releases, not part of the current matching engine. AI-content detection is also coming soon and is intended to appear as a separate signal, so buyers who need that capability now should look elsewhere.

Workflow, privacy, and security

Canvas, Moodle, Blackboard, and Brightspace integrations are offered through LTI 1.3, while the REST API, OpenAPI spec, and webhooks support developer workflows on paid tiers. Noplag says submitted documents are not used to train models or shared between accounts, and offers EU data residency. It encrypts data in transit and at rest, but does not yet hold formal attestations such as SOC 2; organizations that require one should account for that limitation.

Retention depends on the tier: free-check document content is purged after 30 days; paid users can select 30, 60, or 90 days; Enterprise can retain content without a time limit. The Enterprise option may suit organizations with longer retention needs, while those handling sensitive material should weigh the available controls against their own compliance requirements.

Pricing

Noplag is freemium, with a free plan and a 14-day trial. Pro starts at 9.99 USD per month. The plans trade check volume, document size, corpus access, and support level, so the best fit depends on both workload and which sources matter.

Plan	Price	What it includes
Free	Free	3 checks per month, 2,500 words per check, public web and Common Crawl corpus, and community Discord support.
Pro	9.99 USD per month	50 checks per month, 25,000 words per check, Noplag Database, academic index, REST API and webhooks, and email support.
Premium	19.99 USD per month	200 checks per month, 50,000 words per check, Live Web search, branded PDF reports, and priority support with a 12-hour response target.
Enterprise	Custom pricing	Custom check volume, all corpora and Live Web search, on-premises or private-cloud deployment, SSO/SAML, LMS integrations, and dedicated support with an SLA.

Free is enough for occasional, short checks, but its three monthly submissions and 2,500-word ceiling make it restrictive for regular editorial or academic review. Pro is positioned for makers and small teams; its larger quota, academic index, database, and API make it the practical step up for recurring work. Premium targets agencies and publishers that need higher volume, live-web search, branded reports, and faster support. Enterprise is aimed at universities and regulated organizations that need custom volume, deployment choices, identity controls, or an SLA. No seat allowance is stated for the plans, so teams should confirm account needs before choosing.

Free-tier content is purged after 30 days. Paid tiers allow a choice of 30-, 60-, or 90-day retention, while Enterprise permits unlimited retention.

Platforms

Noplag supports web, Windows, macOS, Linux, API, and self-hosted use. That mix gives individuals a browser-based option and organizations deployment and integration routes beyond the hosted service. The API is available on paid tiers; Enterprise adds on-premises or private-cloud deployment and SSO/SAML.

Who it's for

Noplag is best for writers, publishers, small teams, and institutions checking for close textual overlap and needing source-linked evidence. Its academic index and LMS integrations are relevant to education workflows, while the higher quotas and branded reports suit publishing operations. It is not the right primary check for paraphrase or AI-generated text, and the lack of formal security attestations may rule it out for organizations that require them.

Pros and cons

Inspectable evidence: Source links, similarity scores, exact overlapping text, and PDF export help reviewers assess why a match appeared.
Broad source mix: Web, Common Crawl, Wikipedia, academic indexes, the Noplag Database, and user folders cover varied comparison needs.
Useful institutional routes: LTI 1.3 integrations, paid API access, and Enterprise deployment options support larger workflows.
Clear matching boundary: No paraphrase detection, and AI-content detection is still forthcoming, limiting its value for broader integrity screening.
Tier constraints: The free plan allows only three checks monthly at 2,500 words each; regular or longer-document work requires a paid plan.
Security caveat: Encryption and EU data residency are offered, but there are no formal attestations such as SOC 2 yet.

Alternatives

PlagAware is worth comparing for a lower-priced entry point: its free tier includes 10 pages per month and up to 30 monitored URLs with a Content Protection Banner, and its Light plan costs 2.99 EUR per month. Choose it when those page-based checks and monitored URLs suit the work better than Noplag’s source-linked checks and paid academic-index access.

PrePostSEO Plagiarism Checker is a freemium option across web, desktop, and mobile, with API access; its Basic all-in-one annual plan is 4.17 USD per year. Consider it when that broader platform mix or combined tool offering is more relevant than Noplag’s focused matching workflow.

Plagius is a paid option with a free trial and a 6.90 USD one-time Basic license valid for 30 days, for one Windows computer. It is a fit to consider for a short-term, single-computer Windows need; Noplag offers a wider set of platforms and institutional routes.

Copyleaks AI Detector combines AI and plagiarism detection and lists more than 30 AI-detection languages. Choose it when AI screening is a core requirement rather than a forthcoming feature.

Dolos is free, open source under MIT, and offers a web app with ZIP uploads limited to 10 MB. It is an alternative to consider when an open-source option is the priority.

PlagiarismSearch is another freemium plagiarism and AI-submission option. Compare it when that combination better matches the required workflow.

Quetext AI Detector offers a free tier with an AI detector and plagiarism checker each capped at 1,000 words, plus a summarizer and humanizer capped at 2,000 words. It is an option for readers who want those additional tools alongside short checks.

SmallSEOTools Plagiarism Checker has a free plan capped at 1,000 words per scan. Consider it for shorter free scans; Noplag’s free allowance is three monthly checks of up to 2,500 words each.

For more choices, browse Plagiarism Checkers, Plagiarism Detection Software, and AI Plagiarism Checkers.

Verdict

Noplag is a strong choice for writers, publishers, and institutions that need source-linked reports on verbatim and near-verbatim copying, especially when academic sources, APIs, or LMS workflows matter. Its transparent overlap evidence is the main reason to choose it; the inability to detect paraphrase, forthcoming AI screening, and lack of formal security attestations are the main reasons to look elsewhere.

	Noplag	Plag.ai
Free plan	Yes
Free trial	Yes
Paid from	$9.99/mo	€14.95/mo
Platforms	api, Linux, macOS, self-hosted, Web, Windows	Web
Free plan	Yes	Yes
API access	Yes
Paid from	9.99 /mo
Web source matching	Yes
Academic source matching	Yes
Supported languages	5 languages	129 languages
Word limit	2,500 words
Report export formats	PDF
LMS integration	Yes
AI detection		Yes

Noplag vs Plag.ai

Noplag

Plag.ai