Best Free Coding Interview Prep Resources: The 2026 Roundup

You searched "how to prepare for coding interviews." Google returned 847 million results. You now have fourteen tabs open and have learned nothing.

That's the actual problem. Not a shortage of resources. An excess of them, half-overlapping, none explaining what to use in what order. This post is the answer to "just tell me what to do." Here's the stack, what each piece is good for, and exactly where free stops being enough.

Start with a Problem List, Not a Platform

The first decision is not which website to use. It's which curated problem list you're working through. Skip this step and you'll spend a month on LeetCode "just vibing" through random problems and wonder why your performance doesn't improve.

Three lists dominate:

Blind 75 is the original. An ex-Facebook engineer posted it on the Blind forum in 2020. Seventy-five problems, all core patterns, nothing extra. Short enough to finish in three or four weeks. The tradeoff is real: it skips tries, backtracking, and advanced DP entirely. Finish it and you have solid coverage of about 60% of what shows up in interviews.

NeetCode 150 fixes the gaps. Same core 75, plus 86 more problems across six categories Blind 75 ignores: greedy, backtracking, advanced graphs, tries, intervals, and bit manipulation. There's 85% overlap, but the extra 15% covers patterns that show up regularly at FAANG. This is the higher-return list if you have six or more weeks.

Grind 75 is generated algorithmically from the Tech Interview Handbook. You set your available time and it outputs between 75 and 169 problems ranked by frequency and importance. More flexible, less opinionated. Good if you want to dial scope to a specific deadline.

List	Problems	Best for	Main gap
Blind 75	75	Under four weeks, mid-size targets	Tries, backtracking, advanced DP
NeetCode 150	150	Standard prep, FAANG targets	None major
Grind 75	75 to 169	Custom timelines, self-directed learners	Less curated

Start with NeetCode 150 unless you have under four weeks. Then do Blind 75. For a deeper comparison of all three, see the DSA sheet breakdown.

NeetCode: The Best Free Learning Resource, Period

NeetCode.io handles both the problem list and the explanation. Every problem links to a YouTube walkthrough by the same creator. One person. One consistent teaching style. No hunting for which video is actually good.

Those videos are why this resource stands apart. Most DSA explanations are either too slow for engineers or assume too much background. NeetCode's structure is consistent: brute force first, what's wasteful about it, then the better approach and why the invariant holds. No padding. No 20-minute intros.

The channel has over a million subscribers. The walkthroughs for sliding window, two pointers, and dynamic programming are among the clearest on the internet.

The one real gap: NeetCode teaches what a solution looks like, not how to recognize which pattern an unfamiliar problem is asking for. You'll know how to code a sliding window. You might not immediately see that a new problem is a sliding window from its constraints. That recognition layer is where most candidates actually fail.

LeetCode Free Tier: More Than You Think

LeetCode has over 3,000 problems. The free tier gives you access to roughly 1,700. That is more than enough. You will not run out of problems before you run out of prep time.

Premium unlocks company tags, frequency data, and a few locked problems. If you're working through NeetCode 150, all 150 are available for free. You do not need to pay yet.

LeetCode free is sufficient for the actual practice. Premium becomes worth considering two to three weeks out from a specific company's screen.

One thing that's underrated: the discussion section. For any problem you struggle with, the threads often have multiple correct approaches with complexity analysis. Not a substitute for understanding, but a legitimate way to see solutions you wouldn't have found otherwise. Just don't use it as a first resort. Struggle first.

Read the Tech Interview Handbook Before You Open LeetCode

Tech Interview Handbook by Yangshun Tay (ex-Meta) is the clearest single resource for understanding what a technical interview process actually involves. Resume prep, behavioral questions, algorithm strategy, system design overview, and negotiation in one place. Over a million engineers have used it.

It's less a learning resource and more a map. When you don't know what you don't know, start here.

Skipping this step is how engineers spend three months grinding problems without ever practicing communication, behavioral questions, or system design. The map tells you what the typical interview loop looks like, which skills each round tests, and what to study in what order. Thirty minutes reading it will save you weeks of misdirected effort.

System Design: Start with the Primer, Then Build Things

Donne Martin's System Design Primer is a GitHub repository with over 270,000 stars. It covers databases, caching, load balancers, consistency models, message queues, and real-world examples at scale. Anki flashcard decks included.

The System Design Primer covers vocabulary and fundamentals well. It does not have structured walkthroughs of full 45-minute interview problems. Once you've read through it, you need to practice designing complete systems from scratch, not just recalling definitions. Knowing what a CDN is and being able to coherently design YouTube in 45 minutes are very different skills.

For how system design interviews are actually scored, see the system design interview prep guide.

CP-Algorithms: For When You Need the Proof

CP-Algorithms.com translates competitive programming algorithm papers into readable English. Segment trees, Fenwick trees, suffix arrays, number theory. All of it, explained rigorously.

It's not a place to start. It's a place to go when you're stuck on why a particular algorithm works, or when you want the math behind something you've only ever seen implemented. Think of it as the textbook you reach for when the other resources leave you unsatisfied.

If you don't know what a Fenwick tree is, start with NeetCode. If NeetCode's explanation left you unsatisfied, go here. That's exactly what it exists for.

YouTube: What to Watch and What to Skip

Three channels are worth your time. Most others are not.

NeetCode is the obvious pick. Already covered above.

Back to Back SWE has strong coverage of algorithm intuition, particularly for sorting, dynamic programming, and graph traversals. Videos run long but the visual explanations compensate. Good for the problems where you need to see the state transitions to understand what's happening.

Abdul Bari is the best resource for first-principles recursion and time complexity. If your recursive thinking is shaky, watch his playlist before grinding problems. His explanations of why recursion trees work the way they do are better than most textbooks.

Here's the trap, though. Watching a solution feels productive. It's not. Watching a solution is not the same as being able to produce it under pressure. Your brain registers "oh I see how that works" as the same feeling as "I could do that myself" and they are not the same thing.

Watch the video. Close the tab. Open a blank editor. Reproduce the approach from scratch. If you can't, you didn't understand it. You just watched it. This is the core problem with most LeetCode prep. Here's why passive practice doesn't transfer.

Mock Interviews: Pramp Gives You a Starting Point

Pramp was absorbed into Exponent Practice in 2024. The platform still offers free peer mock interviews, with a limit before you hit a paywall.

Peer mocks matter for one reason problem-grinding cannot replace: they train the spoken part. Going silent, failing to explain your reasoning, sounding uncertain while coding correctly. These behaviors get candidates rejected even when the code works. Most candidates are genuinely surprised when they get feedback like this after their first real mock. The code was fine. Everything around the code wasn't.

Grinding LeetCode trains the code. Mock interviews train the part that the rubric also scores.

Five sessions is not enough to plateau. Most candidates need fifteen to twenty before their spoken performance under pressure stabilizes. After the free tier runs out, your options are a paid platform, a study partner who takes it seriously, or continuing to practice unscored.

For context on how much mock volume actually matters, see how many mock interviews you need before your performance levels off.

Where Free Stops Being Enough

Free resources cover the algorithm content, the reference material, and the study plan well. Three things they handle poorly:

Rubric-based feedback. Free platforms tell you whether your code is correct. They don't tell you whether your communication, problem-solving approach, or testing behavior would pass. The actual interview scorecard has four dimensions. You're getting feedback on one of them.

Voice practice at scale. Pramp's free tier covers a few sessions. Most engineers need considerably more before performance under pressure stabilizes. After the free sessions run out, options narrow fast.

Realistic interview pressure. Solving problems alone at your desk is not the same as narrating your thinking to an interviewer while the clock runs. The pressure gap is real, and it shows up in performance. You won't know it's there until you're in a real interview and your mouth stops working.

This is where SpaceComplexity fills in. It's a voice-based AI mock interview platform that gives rubric-based feedback across all four dimensions (communication, problem-solving, code quality, testing) after every session. If the free resources above got you to a solid algorithmic baseline, SpaceComplexity is how you convert that into consistent interview performance.

The Stack

Problem list: NeetCode 150 (or Blind 75 if under four weeks)
Practice platform: LeetCode free tier
Video explanations: NeetCode YouTube
Study guide: Tech Interview Handbook
System design foundation: System Design Primer (GitHub)
Algorithm depth: CP-Algorithms
Mock interviews: Pramp free tier, then something with feedback

Everything else is supplementary. The full tool comparison goes deeper if you want to weigh paid options against each other.