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HackerRank, CodeSignal and Codility: what candidates should know

Most coding online assessments run on HackerRank, CodeSignal or Codility. The problems look similar, but the platforms score you differently, handle hidden tests differently, and offer different practice environments. This HackerRank vs CodeSignal vs Codility guide covers what each one's own candidate help docs say.

Updated Nov 14, 2026 · 6 min read

Details below come from each platform's own help center, checked Nov 14, 2026. Employers configure their own tests (duration, languages, proctoring), so the settings in your invitation take priority over anything general here.

At a glance

HackerRankCodeSignal (GCA)Codility
FormatEmployer-built test: coding, multiple choice, project questions4 questions of varying difficulty, any orderSeveral tasks, usually short programs of 10-20 lines
TimeSet by the employer70 minutes unless the company changes itTypically 30 minutes to 2 hours, one timer for the whole test
ScoringPass/fail per test case, score based on how many pass200-600 Assessment ScoreCorrectness plus performance where it can be measured
What you seeSample cases with expected output; hidden cases show only your outputRun and submit results in the IDE; a README tab explains each verdictOne example test; you can add your own
PracticeSample test from your test login pagePractice area in your CodeSignal accountDemo test and free lessons

HackerRank

HackerRank tests are assembled by the employer, so two can look nothing alike. Project-based questions (front-end, back-end, full-stack, data science) open in an IDE mode with a VS Code or JupyterLab environment.

Scoring. HackerRank's docs say each test case is marked passed or failed, and the overall score depends on the number of test cases passed. Sample test cases are visible, with their inputs and expected outputs, and employers can give them zero points. Hidden test cases show only your output and debug messages, not the expected answer. Partial solutions earn partial credit, but the visible samples alone may be worth nothing.

Limits and languages. HackerRank's execution environment page lists dozens of language versions, each with its own CPU time and memory limits. For example: C and C++ 2 seconds, Java 4 seconds, Python 3 10 seconds, with 512 MB for most. The employer chooses which languages each question allows.

Practice. Every invitation's login page has a "Try Sample Test" option. HackerRank says you can attempt it multiple times, using a different email address each time, and it isn't evaluated.

CodeSignal and the General Coding Assessment

CodeSignal runs both company-specific tests and standardized "certified" assessments. The best known is the General Coding Assessment (GCA): four questions of varying difficulty, 70 minutes, and all questions open from the start. CodeSignal says answers are scored on correctness, speed, implementation and problem solving. You must solve in its IDE; outside IDEs aren't permitted.

Scoring. Certified results produce an Assessment Score from 200 to 600, with higher scores meaning you completed more of the questions. You can submit each question as many times as you like, and CodeSignal keeps your highest-scoring submission, even if a later one had a syntax error. You must submit before leaving a task or your code won't save. Each employer sets its own cut score; CodeSignal doesn't publish a universal passing mark.

Other formats. The Industry Coding Assessment (ICA) is a single project-style question with four progressive levels and a 90-minute limit.

Rules and retakes. During the GCA, CodeSignal allows searches for syntax reference only, such as how to take a substring in Python. Searching for how to solve the problem is not allowed, and neither is AI, even for syntax. Certified assessments have cooldown periods that limit retakes within a 180-day window, and you can share a past score with a new company instead of retaking.

Practice. CodeSignal's practice area (app.codesignal.com/assessments/practice) has one sample of each question type, and companies don't see your activity there. The README tab in the real IDE lists auto-imported libraries for your language and explains each verdict.

Codility

Codility tasks are usually short programs. The timer covers the whole test, can't be paused, and when it runs out, the code in the editor is submitted automatically. Codility says the time you take doesn't factor into automated scoring.

Scoring. Each task is scored for correctness: does it produce correct results for moderate inputs, including corner cases? Where possible, it is also scored for performance: does it stay fast on large data sets? An O(n^2) solution can lose points here even when every answer is right. Code that doesn't compile earns nothing. The example test isn't part of the score, so Codility warns that you can see "OK" on the example and still score 0%. You don't need to validate the input assumptions stated in the task. Style usually isn't scored automatically, though employers may review your code by hand.

Practice. Codility offers a demo test (app.codility.com/demo/take-sample-test) and free programming lessons with exercises. Codility's FAQ points to the demo to show how running and testing code works.

Proctoring settings employers can enable

All three platforms let employers choose how much monitoring a test uses. From their documentation:

  • HackerRank: Copy-paste tracking and tab-switch tracking are built in. Optional modes include Secure Mode (a controlled, full-screen browser), Proctor Mode (copy-paste disabled; webcam, full-screen and tab monitoring; periodic screenshots; candidates consent during onboarding), and a Desktop App mode with operating-system-level monitoring. Image proctoring, photo ID and AI plagiarism detection are also available.
  • CodeSignal: Proctored assessments ask you to share your camera, microphone and screen and to show a government photo ID. CodeSignal's own team reviews the recording. It says proctoring data isn't shared with the hiring company and is deleted within 15 days, and that proctoring doesn't affect your score. The timer starts only after setup.
  • Codility: Proctoring is off by default. Employers can turn on logging of paste events and tab switches, flags for unusually fast completion or copying the task text, webcam snapshots (kept 30 days), and optional screen or video recording. Candidates see a disclosure on the intro page. Codility tells employers that not every signal is evidence of wrongdoing.

Rules on outside help differ by platform and employer. Codility says you must work on your own. CodeSignal limits the GCA to syntax lookups. Read the policy in your invitation and follow what you agreed to.

Practical tips for any platform

  • Take the platform's practice test in the language you'll actually use.
  • Read the constraints before coding. Large inputs mean hidden tests or performance tests will reject a quadratic solution.
  • Write your own test inputs: empty, single element, duplicates, extremes and one large case. Visible examples prove little.
  • Submit a working brute force early, then improve it. Partial credit is real on all three platforms, and CodeSignal keeps your best submission.
  • On a four-question GCA, don't let the hardest question eat the clock. Lock in points where you can first.

For what to practice, see our problem list comparison, and for one company's OA end to end, the Amazon online assessment guide. Interview LLM can help in practice: screenshot a practice problem after you've tried it, get a worked solution with complexity analysis, then re-solve it from scratch.

Sources (checked Nov 14, 2026)

FAQ

Do partial test cases count?

On all three, generally yes. HackerRank says your score depends on the number of test cases passed. CodeSignal's 200-600 score rises as you complete more requirements and test cases. Codility scores each task on correctness tests and, where it applies, performance tests. The example tests you can see may count for little or nothing.

Can I reuse a CodeSignal GCA score?

Often, yes. CodeSignal lets you share a past certified score with companies that request one. Retakes are limited by cooldown periods, and you can't make more than one attempt per invitation.

Can I write code in my own IDE and paste it in?

It depends on the platform and the employer. CodeSignal's GCA says outside IDEs are not permitted. Codility says to follow your test's policy and, if allowed, run the pasted code to check it compiles. HackerRank and Codility both log paste events in the report employers see.

Which platform is the hardest?

None of them is harder by design. Difficulty comes from the questions the employer picks. The scoring rules differ, though: Codility's performance tests reward efficient solutions, and CodeSignal's time-boxed, four-question GCA counts speed in its scoring.