Codility Test: How It Works, How It's Scored and How to Prepare

Codility test explained: task types, time limits, how correctness and performance are scored, the demo test and the rules on AI.

A Codility test is one of the most common first steps in technical hiring, and it is also one of the least explained. The invitation gives you a link and sometimes a deadline, and questions such as whether speed counts, whether the green "OK" means you passed and whether you may use your own editor are left for you to discover during the test.

We wrote this for developers who have received a Codility invitation and want to understand the test before the timer starts. It covers what the test is, the kinds of task it contains, the time limits, how correctness and performance are scored, the languages on offer, the demo test, what you see before you begin, live interviews on Codility, and the AI assistant that some employers switch on. We make Verve AI, an interview copilot, and what we say about Codility comes from its own documentation as it stood in October 2026.

In brief, a Codility assessment is a timed set of tasks that are scored automatically against hidden test cases after you submit. The time you take does not affect the automated score, a solution that does not compile earns nothing, and the employer decides which outside resources are allowed.

What is a Codility test?

Codility's candidate FAQ describes its screening assessments as an evaluation of job-related technical skills. You are asked to solve several problems by writing code, modifying code or answering technical questions, your responses are scored automatically once submitted, and the results go to the test administrator at the hiring company.

The test runs in a browser on a laptop or desktop computer. Codility lists recent versions of Chrome, Edge, Firefox, Opera and Safari as supported and says phones and tablets are not. Some employers require the Codility App instead, and in that case you are asked to download and install it before you can begin.

What kinds of task are in the assessment?

The employer builds the test from Codility's task library, so no two companies need to send the same one. Codility says each assessment consists of several tasks, that programming tasks usually call for short programs of 10 to 20 lines, and that the tasks are chosen to reflect skills the role needs.

Its library documentation groups the tasks into three families, which gives a fair idea of what you might meet.

• Problem-solving tasks are language-agnostic and include algorithmic tasks, general coding tasks and bug-fixing tasks, where you correct working code by changing only a few lines.
• Real-life tasks use a specific language or framework, such as React for front-end roles or Spring for back-end roles, and are based on everyday development scenarios.
• Technical knowledge is tested with multiple-choice question sets on a topic such as AWS or Git, typically ten questions long.

How long does it last, and can you pause it?

Codility says its assessments typically last between half an hour and two hours, with the exact limit set by the employer according to the number of tasks. The limit shown on screen is for the whole assessment and not for a single task, so dividing the time is your decision.

Once you press Start, the timer cannot be paused or stopped, which is why Codility tells candidates to complete the test in one sitting. When the time runs out, whatever code is in the editor is submitted automatically and the assessment ends.

One statement in the FAQ surprises many candidates. Codility says its assessments are designed to allow plenty of time, and that the time you take to solve the tasks does not factor into automated scoring.

What do you see before you start?

You can open the invitation link without starting the test, and it is worth doing as soon as the email arrives. The introductory page shows how many tasks there are, how much time you have, which languages are permitted, and the assessment policies set by the testing team.

That page is also where you learn about monitoring. Codility says the events it tracks depend on the policies of the testing team, and that some tests require access to your screen or camera. What those settings record is covered in our article on what coding platforms monitor.

How is a Codility test scored?

Codility's scoring principles explain that scoring is based on test cases. You are given an example test case that does not count, and after submission your solution is graded against further cases of a similar nature. Every task has at least six of them, and the task score is the share you pass, so a solution that fails four cases out of ten scores 60%.

The test cases come in two kinds, and both can apply to one task. Correctness cases check that the solution meets the requirements, including corner cases, and they apply to every task. Performance cases check how the running time grows as the input gets larger, and they apply to tasks that ask you to write an algorithm.

Three consequences follow from this, and each is stated in the candidate FAQ.

• The "OK" you see after pressing Run only confirms that the code compiles and passes the example case.
• A final submission that does not compile cannot be assessed and earns no points for that task.
• Coding style usually does not affect the automated score, although some tasks are designed to assess it and a reviewer may read your code.

Whether you see your result is up to the employer. Codility says some hiring teams share results with candidates and others keep them confidential.

Which languages can you use?

The languages are set task by task, and the list for your test appears on the introductory page. Codility notes that unless a task is language-specific, the language you choose does not factor into the score, so pick the one you write most fluently.

Its demo test gives a sense of the range. When we checked, it listed C, C++, C#, Dart, Go, Java, JavaScript, Kotlin, Lua, Objective-C, Pascal, Perl, PHP, Python, Ruby, Rust, Scala, Swift, TypeScript and Visual Basic. You may use only the standard libraries of the language unless the task description says otherwise.

What is the Codility demo test?

The demo test is a free sample assessment with one task and a 30-minute limit, and Codility says you can take it as many times as you like. It uses the same editor as a real test, so it is the quickest way to learn how Run, custom test cases and Submit behave.

A few habits are worth practicing there, because Codility recommends them for the real thing. Read every task first, keep the function signature exactly as given, test with empty, very small and very large inputs, and press Submit only when you are sure, because a submitted solution cannot be changed.

What are the rules on outside help and AI?

Codility's own rule is narrow, and the rest is left to the employer. The FAQ says you must work on your own and may not seek help from other people. For books, websites and other resources, it tells you to review the assessment policies included with your test link.

The same policy governs whether you may use your own editor. Where the employer permits it, you can write a solution in an IDE of your choice and paste it into the Codility interface, and otherwise you work in the browser editor.

Some tests include an AI assistant by design. Codility has a chat-based assistant called Cody, which the employer can enable for a test or an interview. Codility says candidates can use it to clarify the task or ask for documentation-style references, and that the hiring team can review the complete transcript of the conversation.

How do Codility live interviews work?

Codility also offers a live product, which it describes as a collaborative video programming platform for technical interviews and pair programming. You can enter the session once the interviewer has started it. Where the assistant is enabled in an interview, the interviewer has a read-only view of your conversation with it.

A live round is a conversation as much as a test, since the interviewer can ask why you chose an approach and what it costs. If your process uses a different platform for the first screen, our guide to the CodeSignal assessment explains how that one is structured.

How does Verve AI help with the rounds after a Codility test?

A good result usually leads to a technical interview with a person, and the skill that round tests is explaining your reasoning aloud. Verve AI's mock interviews are spoken sessions with an AI interviewer, drawn from a question bank, your own questions or the job description, and each one ends with a report.

For live coding interviews, the Coding Copilot captures a problem from the screen with a hotkey and returns an approach, code and an explanation, and it can debug code you have written. It shares one context with the live audio, so a follow-up question is answered about the same solution, and its suggestions are prompts for answers given in your own words.

For the timed assessment, follow the policies shown on your test's introductory page, because the employer sets them. You can start on Verve AI's free plan to rehearse the interview that follows.

FAQ

How long does a Codility test take?

A Codility test typically lasts between half an hour and two hours, according to Codility's candidate FAQ. The employer sets the exact limit, which covers the whole assessment and is shown on the introductory page before you start.

Does time affect your Codility score?

Codility states that the time you take to solve the tasks does not factor into its automated scoring. The time limit still matters, because the code in the editor is submitted automatically when the timer reaches zero.

Why did I score low on Codility after passing the example test?

The example test on Codility does not count towards the score. Your solution is graded after submission against additional correctness cases, and for algorithmic tasks against performance cases with large inputs, so code that passes the example can still fail many of them.

Can you use your own IDE on a Codility test?

Codility says you should follow the policy communicated with your test. Where the employer permits it, you can write the solution in your own editor and paste it into the Codility interface, then press Run to confirm that it compiles there.

Can you retake the Codility demo test?

The Codility demo test can be taken as many times as you like. It contains one task with a 30-minute limit and uses the same editor as a real assessment, which makes it suitable for learning the interface.