The free AI-mock lane got crowded fast in 2026. Type the phrase into any search engine and you get pages of tools promising a realistic interview with instant AI feedback, free. Most of them share one quiet limitation: they never execute anything. They record what you said, transcribe it, and grade the transcript. The code you wrote — if you wrote any at all — is read by a language model the same way it reads an essay, and never compiled, never run, never tested against a single input.
That distinction sounds technical. It is actually the whole game, because the real coding round you are preparing for does exactly one thing with your solution: it runs it.
What "the AI grades how you sounded" actually means
A transcript grader scores structure and delivery: did you restate the problem, did you narrate a plan, did you mention complexity, did you sound confident. Those are real skills and worth practising — a scored conversation is genuinely useful for the intro and behavioral rounds, and for learning to think out loud.
The blind spot is that a model reading your code makes the same mistake you do when you re-read your own code: it evaluates the version you meant to write. Plausible-looking code with an off-by-one error, a missed empty-input case, or a loop that never terminates on the maximum input reads fine in a transcript. It fails in an exam hall. A grader that never runs anything cannot tell you which of those two candidates you are — and that is precisely the information a mock exists to give you.
The five-question checklist
Before you spend a week of prep inside any no-cost mock-interview tool, check five things.
1. Does it execute my submission? Not "analyse", not "review" — execute. If you cannot find a clear yes, the answer is no.
2. Does it run my code against test cases I did not write, including edge cases — empty input, one element, all-identical values, the maximum size, zeros and negatives? Sample-case-only checking is how solutions that are 80 percent right feel 100 percent done.
3. Does it return a verdict per test — Accepted, Wrong Answer, a runtime error — rather than a paragraph of impressions? A verdict is checkable; an impression is a vibe.
4. Can I pick the language I will actually use in the exam? Practising in one language and sitting the test in another resets half your muscle memory.
5. Does the scored conversation exist as well? Execution without a scored interview is a judge, not a mock. You want both surfaces: the conversation for how you explain, the judge for whether it runs.
Why "did it run" is the one signal that cannot be faked
A polished resume can be written for you. A smooth voice answer can be rehearsed until it hides the gaps. A confident walkthrough of broken code is one of the most common sights in real interviews — the candidate believes it works, the interviewer runs it, and the room goes quiet.
Pass-or-fail against hidden test cases is the one prep signal with no cosmetic version. Either the output matched or it did not. That is why real hiring loops at every level — from mass-drive coding rounds like the TCS NQT to product-company onsites — are built around execution, and why practising without it systematically overestimates your readiness. The candidates who discover this on exam day paid the highest possible price to learn a fact a free tool could have told them in week one.
How a real judge changes your prep
The loop becomes: write, submit, watch it fail on an input you did not consider, fix it, resubmit, watch it pass. Instant Accepted / Wrong Answer feedback turns every practice problem into a small exam with a real result, and the scorecard on top tells you how you explained it. Over two weeks that loop quietly fixes the habits transcript grading cannot see — testing before declaring done, handling the ugly inputs first, reading the problem twice.
On placd the two surfaces are split exactly this way: the practice problems at placd.in/problems run in an in-browser judge that executes your code against real test cases, and the AI mock interview at placd.in/products/mock-interview is the scored conversation — role-specific rounds, typed, ending in a verdict (Pro; the free 2-minute readiness check at placd.in/readiness gives you a scored taste of it first). If you are targeting a specific drive, the company banks at placd.in/companies/tcs and placd.in/companies/amazon keep the questions close to what that loop actually asks, and the roadmaps at placd.in/roadmaps pace the whole thing so the judge work and the mock reps land in the same weeks.
FAQs
Is a transcript-graded mock useless? No — it is half the preparation. Communication is scored in every real loop, and a scored conversation is the right tool for it. It becomes a problem only when it is presented as full interview prep and the execution half silently does not exist.
Do free tiers ever include a real judge? Rarely, which is why it is worth checking before you commit a prep cycle. placd's free tier includes the in-browser judge on practice problems and the 2-minute readiness check, no card required; the full scored AI mock is part of Pro.
What if my exam is days away? Prioritise the judge. In the last week, the highest-value hour is submitting timed problems against real test cases in your exam language — it is the closest legal rehearsal of the actual event.