- AI code detectors side by side
- Ten tools that check code for AI authorship
- Snippet checker, classroom scanner or repository tool?
- Why a code detector result is a signal, never proof
- Matching the detector to the job in front of you
- Questions to ask before you upload any code
- My advice on checking code for AI
- Frequently asked questions
The best AI code detector depends on who's checking. Free paste-in checkers suit a quick look at one snippet, classroom tools check student submissions file by file, engineering tools track AI-written code across repositories, and one open source option runs on your own machine. Every one of them gives a likelihood, not proof. Ten options follow in no particular order.
AI coding assistants now write a lot of the code people hand in, merge or ship, so teachers, team leads and clients want to know where it came from. The tools that answer that question aren't all built for the same person, and picking the wrong kind wastes an afternoon.
This list is about detecting AI-written code, not reviewing it for bugs. The ten tools are listed alphabetically, in no particular order, and each description comes from the vendor's own page, read as of Nov 2026.
AI code detectors side by side
| Tool | Type | Good for |
|---|---|---|
| AI Code Detector (aicodedetector.com) | Free paste-in code checker | Quick check of one snippet |
| AICodeDetector.org | Free online code checker | Named AI assistants and common languages |
| AICodePlag | Detector suite with a code tool | Code, text and images in one login |
| Codect | Open source detector | Running it yourself |
| Codequiry | Code plagiarism and AI code checker | Classroom code checks |
| CodeSpy | AI code risk scanner | A visual heatmap of likely AI code |
| Copyleaks | AI detection suite with code tools | Code license checks plus AI detection |
| Decopy AI Code Detector | Browser-based code detector | A report on pasted code |
| Overchat AI Code Detector | Code detector inside an AI chat site | Screening pull requests |
| Span | Engineering analytics detector | Chunk-level detection in repositories |
Ten tools that check code for AI authorship
AI Code Detector (aicodedetector.com)
Best for: Pasting a snippet to see which language it's in and whether it looks AI-generated, from a site that says it gives no legal or definitive proof.
AICodeDetector.org
Best for: Checking whether code came from ChatGPT, Claude, GitHub Copilot or a person, across Python, JavaScript, PHP, C/C++ and Java.
AICodePlag
Best for: Analyzing programming code for AI patterns inside a suite that also covers AI text, AI images and grammar checks.
Codect
Best for: Developers who'd rather run an open source detector for AI-written code, listed under a GPL-3.0 license on GitHub, than upload code to a website.
Codequiry
Best for: Teachers who want AI-written code flagged file by file next to plagiarism checks, with a desktop app as well.
CodeSpy
Best for: Seeing a visual heatmap of likely AI code in JavaScript, Python, Java, PHP, C/C++ or C# before you create an account.
Copyleaks
Best for: Teams that want license compliance checks and AI code detection from a company that also detects AI text, images and video.
Decopy AI Code Detector
Best for: Getting a report that highlights code segments that may be AI-generated, from a browser tool aimed at learners, project teams and code reviews.
Overchat AI Code Detector
Best for: Screening code or open-source pull requests for AI-generated contributions, with a free detector on a site that also offers AI chat, image and video tools.
Span
Best for: Engineering leaders who want AI-assisted and human-written code told apart at chunk level, to see how much AI code reaches production.
Snippet checker, classroom scanner or repository tool?
Put the vendor pages next to each other and the split is plain. aicodedetector.com says 'The tool doesn't give legal or definitive proof', a line worth reading before you trust any score. AICodeDetector.org says it 'identifies whether code is written by AI tools', and AICodePlag offers a way to 'Analyze programming code for AI patterns' inside a wider suite.
Codequiry invites you to 'Flag AI written code, file by file' offers a desktop app and lets you 'Check your class free', so it's built around student submissions. Span describes its model as one for 'chunk-level detection of AI generated code', for engineering leaders who want to see AI code across repositories. CodeSpy promises to 'Pinpoint the AI in your codebase', and Copyleaks' page is titled 'Code License Compliance & AI Code Detection'.
Codect is listed under a GPL-3.0 license on GitHub, which makes it software you run yourself rather than a website you paste into. That's the split a reader wouldn't guess: some tools are free paste-in checkers for one snippet, one is built around student submissions, one is built for engineering leaders watching repositories, and one is open source software you run on your own machine.
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Why a code detector result is a signal, never proof
Code is harder to judge than prose. Short functions look alike whoever wrote them, style guides and linters push human code towards the same tidy patterns an AI model produces, and a developer who edits AI output by hand blurs the line further. Some vendors publish accuracy claims of their own, but those are the vendors' own numbers, and none of them can tell you how a particular file was written.
So treat a high score as a reason to ask a question, not as an answer. Ask the student to walk you through the logic, ask the contractor how the code was produced, or look at the commit history. A person who wrote the code can usually explain why it's shaped that way.
Matching the detector to the job in front of you
- One snippet, right now. A free browser checker is enough when you want a quick read on a piece of code someone sent you. Paste it, read the result, and don't treat it as more than a hint.
- A class set of assignments. Teachers need file-by-file results, a way to check a whole class at once and a plagiarism check alongside the AI one, because copying from a classmate and copying from a chatbot often show up together.
- A team's repositories. Engineering leaders are usually asking how much AI-assisted code reaches production, not whose work it might be. That needs a tool that reads code at chunk level across repositories rather than one snippet at a time.
- Licensing. If the worry is code that carries a license you can't ship, look for a tool that checks license compliance as well as AI origin.
- Privacy. Pasting proprietary code into a website sends it to someone else's server. If that's a problem, an open source detector you run yourself keeps the code on your own machine.
Questions to ask before you upload any code
- Which languages does it support, and does it cover the one you use?
- Does it store the code I paste, and for how long?
- Does it show which lines or sections look AI-written, or only one overall number?
- Can it check a whole folder or class set, or one snippet at a time?
- Does the vendor say plainly that its result is a likelihood rather than proof?
If you write code with AI yourself, my list of AI coding assistants covers the tools on the other side of this question.
Do you make an AI code detector? Tool makers can ask to be considered for a featured place on this list.
My advice on checking code for AI
Decide what you're protecting first. If it's fairness in a class, pick a tool built for student submissions and use its result to start a conversation. If it's visibility across a codebase, pick an engineering tool that works across repositories. If it's a quick sanity check, a free paste-in checker is fine, and if the code can't leave your machine, run an open source detector yourself. Whichever you choose, never treat a score as the final word.
For the review side of AI code, my AI prompts for code review help you check what the code does, whoever wrote it.
Want your tool on this list? Featured spots and reviews here are paid partnerships. Here's how to partner with me.
Frequently asked questions
Can an AI code detector prove code was written by AI?
No. Every tool here gives a likelihood based on patterns, and at least one vendor says on its own page that its result isn't legal or definitive proof. Use the result to ask questions, not to settle them.
Are there free AI code detectors?
Several tools on this list offer a free paste-in check or a free scan on their own pages, as of Nov 2026, and one is open source. Free limits change, so check the vendor's site before you rely on one.
Which programming languages do AI code detectors support?
Most cover the common ones, such as Python, JavaScript, Java, PHP and C or C++, and some add C#. Check the vendor's list if you work in a less common language.
Is it safe to paste private code into an online detector?
That depends on the vendor's storage policy, so read it first. If the code is confidential, an open source detector you run on your own computer avoids sending it anywhere.
What's the difference between an AI code detector and a plagiarism checker?
A plagiarism checker compares code with other sources to find copies. An AI code detector looks for patterns typical of machine-written code. Classroom tools often do both, because the two problems tend to turn up together.
Can AI code detectors spot code that a person has edited?
Less reliably. Once a developer rewrites, renames and restructures AI output, the patterns detectors look for fade, which is one more reason a score should start a conversation rather than end one.
