DesignDojo vs HelloInterview
HelloInterview is the most polished paid product in the system-design interview space. DesignDojo is a free, open-source, bring-your-own-key alternative. Same problem domain — different tradeoffs.
DesignDojo is not endorsed by or derived from HelloInterview. HelloInterview's features and pricing change over time — verify current details on their official site before relying on the comparison below.
- You learn best from polished video walkthroughs.
- You want a curated catalog with consistent production quality.
- A monthly subscription doesn't bother you.
- You'd rather not deal with AI provider setup.
- You want it free, no subscription, ever.
- You want to choose which AI grades you (BYOK or local).
- You want all your prep data on your own laptop.
- You like open-source projects you can fork.
Feature-by-feature
Last verified May 2026. HelloInterview features and pricing change — see their site for current details.
| Feature | HelloInterview | DesignDojo |
|---|---|---|
| Pricing | Paid subscription | Free, forever |
| AI provider | Built-in (bundled with subscription) | BYOK — your OpenAI / Anthropic / Gemini / OpenRouter / Groq / Ollama |
| Cost per session | Bundled into subscription | ≈ $0.0001 on cheap models, $0 with local Ollama |
| Open source | Closed | MIT licensed on GitHub |
| Problem library | Large catalog of HLD + LLD problems with video walkthroughs | 30+ HLD + LLD problems, growing. Written walkthroughs, no video yet. |
| AI tutor / mock interviewer | Yes — proprietary AI mock interviewer | Yes — stage-by-stage AI tutor that grades against a senior rubric |
| Whiteboard | Custom in-app whiteboard | Excalidraw, embedded |
| Code editor (LLD) | Yes | Yes — Monaco editor, multiple languages |
| Video lessons | Yes | No — written walkthroughs only |
| Mobile practice | Limited (interactive practice needs a computer) | Reading on mobile fully supported; practice mode needs ≥1024px |
| Account required | Yes | No — nothing to sign up for |
| Data location | On their servers | Your browser (IndexedDB) + your AI provider directly |
Frequently asked
Is DesignDojo affiliated with HelloInterview?
No. DesignDojo is not affiliated with, endorsed by, sponsored by, or derived from HelloInterview. We are a separate, independent open-source project. The two products solve a similar problem in different ways.
Did you copy any content, problems, or rubrics from HelloInterview?
No. Every problem statement, rubric, walkthrough, and AI prompt on DesignDojo was written from first principles for this project. Where we use a stage-by-stage interview structure (requirements → estimation → API → data → high-level design → deep dives), that structure is industry-standard for senior system-design coaching and predates either of our products — you'll find the same shape in canonical references like the System Design Primer, Designing Data-Intensive Applications, and many free engineering blogs. The format is shared; the words are ours.
Why mention HelloInterview at all then?
HelloInterview is the most well-known paid product in this space, and many engineers reach DesignDojo searching for a cheaper or open-source alternative. This page exists to help those searchers compare honestly and decide what fits their budget and learning style — not to put down a tool that many people get value from.
Should I use one or the other?
Use whichever helps you ship a better interview. HelloInterview has polished video content and a curated catalog — if you learn best from video and don't mind a subscription, you may prefer it. DesignDojo is the right pick if you want free, want to control which AI does your grading, want everything to stay on your laptop, or want to hack on the project itself. There's no rule against using both.
Try DesignDojo free
No account, no email, no card. Pick a problem and bring your AI key.