Show HN: I built a small browser engine from scratch in C++ (github.com)
Hi HN! Korean high school senior here, about to start CS in college.
I built a browser engine from scratch in C++ to understand how browsers work. First time using C++, 8 weeks of development, lots of debugging—but it works!
Features:
- HTML parsing with error correction
- CSS cascade and inheritance
- Block/inline layout engine
- Async image loading + caching
- Link navigation + history
Hardest parts:
- String parsing(html, css)
- Rendering
- Image Caching & Layout Reflowing
What I learned (beyond code):
- Systematic debugging is crucial
- Ship with known bugs rather than chase perfection
- The Power of "Why?"
~3,000 lines of C++17/Qt6. Would love feedback on code architecture and C++ best practices!
23 comments
[ 2.2 ms ] story [ 38.9 ms ] thread_simple_ http server is a few lines of code in Python. It's an easy way to add remote access to application. Just ask any advanced LLM.
Well done.
People making all sorts of libraries for HTML/CSS parsers, render trees, layout models etc.
I don’t want to see a world where everything runs on top of Chromium and we all just unwittingly submit to it.
I had AI help me with:
- Initial layout calculation logic (the layout concept was new to me)
- Catching edge cases in the parser
- Recent refactoring for code quality
But I designed and coded myself:
- The overall rendering pipeline architecture
- CSS parser from scratch
- Debugging
- All architectural decisions
As for understanding - I don't know what understanding exactly is. But I think it means how familiar you become with a concept. By that definition, yes, I understand how the rendering pipeline, parsers, layout tree etc work.
First time using C++, so I needed guidance on concepts I'd never seen before. But the learning, problem-solving, and persistence were mine.
Thanks for asking!
The amount of learning this person has done is incredible. Kudos.
I also appreciated seeing they used AI and tutorials yet fixed bugs themselves, as a way to demonstrate they understood I the code.
(Speaking as someone who also started writing my own long ago, and it's far from complete.)
Your project feels phenomenal. Definitely starred.
I was actually trying to create a browser (in golang) myself as well (using LLM assistance) & I really couldn't do it after countless efforts.
https://github.com/SerJaimeLannister/golang-browser Much of it was just curiosity towards if LLM's could port the rust project by emsh https://emsh.cat/one-human-one-agent-one-browser/ into golang & this has led to some really insightful discussions between me and emsh on bluesky
This is actually really pretty cool as I was targeting a ~10k loc for golang from the ~20k loc of rust (given how golang has networking binaries and other stuff)
I guess this is really cool. I was always really averse to C++ preferring golang. I think I am ken-thompson pilled for the most part lol.
Anyways its really great to see people my age working in similar ideas. Somehow it gives us I guess a more sense of connection like I am not alone doing these things and I guess its pretty cool feeling seeing others do similar stuff and learning from them!
I have starred your repo and good luck for college too man! Hope to communicate with ya.
Edit: Another comment here as someone here mentioned that you used LLM, which LLM did you end up using and how'd you use it. For me personally, the most (success?) that I found which could generate a hackernews without any styles and anything was via their computer-use agent model (which I am thinking of downloading & working with kimi-cli to add more styling and other stuff as well in golang just out of curiosity)
I don't really mind if you used LLM, but I am curious as to how in this instance.
You realise that it's only a toy implementation aimed at learning and not a full implementation. The parsing of HTML alone is way more complex than your actual implementation not mentioning at lot of things like the rendering or network (outsourced to Qt).
Still a nice achievement that get you to understand why making a browser is a very complex task.