Show HN: I built a small browser engine from scratch in C++

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!

GitHub: https://github.com/beginner-jhj/mini_browser

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userbinator 9 minutes ago | parent | next [-]

Interesting to see everyone seemingly writing their own browser lately. Ironic to think that AI assistance, from Google itself, might be what ends up breaking their browser monopoly.

(Speaking as someone who also started writing my own long ago, and it's far from complete.)

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vintagedave an hour ago | parent | prev | next [-]

> I had to implement recursion, which I wasn't familiar with.

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.

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robshippr an hour ago | parent | prev | next [-]

Incredible job here. Really took a lot of work to get this done. Keep it up.

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grougnax 2 hours ago | parent | prev | next [-]

This might be the hardest thing ever in computer science, kudos!

	▲	solusipse an hour ago \| parent [-]
		lol

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butz an hour ago | parent | prev | next [-]

Good job! You should consider contributing to a similar small browser - Dillo @ https://dillo-browser.org/ , and help to build a complete tiny browser.

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noo_u 3 hours ago | parent | prev | next [-]

This is a really awesome project! If you have time/interest, you could try to build a simple http server now, that your browser could communicate with. Then you could try to implement a simple version of TCP/IP, and look into how lower level networking works. Great job!

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zabzonk 2 hours ago | parent | next [-]

In my experience, not a good idea to write both the client and the server for a given protocol which use each other. Far too easy to misunderstand the protocol. I remember doing this for a training course I wrote for OLE (later COM) years ago. The client and the server worked perfectly together, just not with correctly implemented OLE clients and servers.

	▲	snerbles 31 minutes ago \| parent [-]
		Just slap a new legally-distinct-but-still-confusing name on your client/server pair, and use it as a marketing tool to sucker in purchasing managers. Like EtherNet/IP, where the IP somehow stands for "Industrial Protocol".

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rustyhancock 2 hours ago | parent | prev [-]

The real full stack engineering

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ge96 2 hours ago | parent [-]

But did they make their own CPU?

	▲	aruametello 2 hours ago \| parent [-]
		... did they mine their own minerals? this could go into a sagan's "If you wish to make an apple pie from scratch, you must first invent the universe."

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xacky 3 hours ago | parent | prev | next [-]

I follow a lot of the alternate browser engines and am always looking for new ones outside of the big three. You should use your experience to get a career in the browser tech world as we are dangerously close to the Chromium only web.

	▲	skybrian 2 hours ago \| parent [-]
		I think this is cool as long as you don't use it to do your banking, and it needs to be running in a VM or on a Raspberry Pi or something. The Internet is dangerous. Something something don't write your own crypto. Also, there's a big difference between running a handmade browser that I wrote and trusting one that some stranger wrote. I guess I'm going to have to try writing my own someday :-)

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lasgawe 2 hours ago | parent | prev | next [-]

This is one of the hardest projects of its kind. Congrats! looks cool.

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lifetimerubyist 3 hours ago | parent | prev | next [-]

Cursor is a 30 billion dollar corporation that couldn’t do this with practically unlimited compute for their AI.

Well done.

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samiv 2 hours ago | parent | prev | next [-]

Since when does homework feature on the front page of HN? I find this very odd...

	▲	antirez 2 hours ago \| parent \| next [-]
		Probably more complex project than projects 99% of what software developers with a real job do daily.
	▲	dag11 2 hours ago \| parent \| prev \| next [-]
		What high school CS class (or even college class) is assigning a project to implement a minimal web renderer? This is super impressive.
	▲	ikamm 2 hours ago \| parent \| prev \| next [-]
		Nowhere in the post does OP say this is a homework assignment. All they said was that they are a high school senior.
	▲	lotusw0w an hour ago \| parent \| prev [-]
		Name one college/university program with homework as impressive as this. This is a serious request

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pipeline_peak an hour ago | parent | prev | next [-]

We need more projects like this.

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.

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quentindanjou an hour ago | parent | prev | next [-]

How much was coded with an LLM and how much do you understand?

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forgotpwd16 an hour ago | parent [-]

Excluding recent refactor commits code seems to be handwritten, maybe lightly AI-assisted.

	▲	quentindanjou 6 minutes ago \| parent \| next [-]
		I am not sure on what you are basing this. Even the post itself looks written by an LLM. I might be wrong, things are always evolving and it is going to be more and more difficult to spot. But I was genuinely asking OP, and I don't have the intention of undermining their achievement! (it stays cool even with use of LLM)
	▲	FEELmyAGI 28 minutes ago \| parent \| prev [-]
		Based on what? In fact, the commit messages sure make it seem like someone who only knows how to use git to to take snapshots, exactly like when one turns off their brain and vibe codes, and after chatting enough with the chatbot to get their next feature seemingly to work make some sort of "updated bla" commit with no reference to the extremely detailed code change they just made. https://github.com/beginner-jhj/mini_browser/commits/main/

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luskira 3 hours ago | parent | prev | next [-]

this is so cool man congrats!

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olliem36 an hour ago | parent | prev [-]

Did you use GPT 5.2 Codex? lol