Show HN: An interactive guide to how browsers work(howbrowserswork.com) |
Show HN: An interactive guide to how browsers work(howbrowserswork.com) |
Early browsers without DOMs (with initial release date): WorldWideWeb (Nexus) (Dec 1990), Erwise (Apr 1992), ViolaWWW (May 1992), Lynx (1992), NCSA Mosaic 1.0 (Apr 1993), Netscape 1.0 (Dec 1994), and IE 1.0 (Aug 1995).
Note: Lynx remains a non-DOM browser by design.
AOL 1.0–2.0 (1994–1995) used the AOLPress engine which was static with no programmable objects.
The ability to interact with the DOM began with "Legacy DOM" (Level 0) in Netscape 2.0 (Sept 1995), IE 3.0 (Aug 1996), AOL 3.0 (1996, via integrated IE engine), and Opera 3.0 (1997). Then there was an intermediate phase in 1997 where Netscape 4.0 (document.layers) and IE 4.0 (document.all) each used their own model.
The first universal standard was the W3C DOM Level 1 Recommendation (Oct 1998). Major browsers adopted this slowly: IE 5.0 (Mar 1999) offered partial support, while Konqueror 2.0 (Oct 2000) and Netscape 6.0 (Nov 2000) were the first W3C-compliant engines (KHTML and Gecko).
Safari 1.0 (2003), Firefox 1.0 (2004), and Chrome 1.0 (2008) launched with native standard DOM support from version 1.0.
Currently most major browser engines follow the WHATWG DOM Living Standard to supports real-time feature implementation.
No, I don't think so. I don't know why the GP comment is at the top beyond historical interest. If you continue with your plans mentioned elsewhere to cover things like layout, rendering, scripting, etc, under this standard almost everything will have to have the "in modern browsers" added to it.
Part of the problem is the term "DOM" is overloaded. Fundamentally it's an API, so in that sense it only has meaning for a browser to "have a DOM" if it supports scripting that can use that API. And, in fact, all browsers that ever shipped with scripting have had some form of a DOM API (going back to the retroactively named DOM Level 0). That makes sense, because what's the point of scripting if it can't interact with page contents in some way?
So, "Lynx remains a non-DOM browser by design" is true, but only in the sense that it's not scripted at all, so of course it doesn't have DOM APIs, the same way it remains a non-canvas browser and a non-webworker browser. There's no javascript to use those things (it's a non-cssanimation browser too).
There's a looser sense of the "DOM", though, that refers to how HTML parsers turn an HTML text document into the tree structure that will then be interpreted for layout, rendering, etc.
The HTML spec[1] uses this language ("User agents must use the parsing rules described in this section to generate the DOM trees from text/html resources"), but notes it's for parsing specification convenience to act as if you'll end up with a DOM tree at the end of parsing, even if you don't actually use it as a DOM tree ("Implementations that do not support scripting do not have to actually create a DOM Document object, but the DOM tree in such cases is still used as the model for the rest of the specification.")
In that broader sense, all browsers, even non-modern ones (and Lynx) "have a DOM", since they're all parsing a text resource and turning it into some data structure that will be used for layout and rendering, even if it's the very simple layouts of the first browsers, or the subset of layout that browsers like Lynx support.
If you like it might be nice to include a section on historical and/or niche browsers that lack some of the elements this guide describes - like e.g. Dillo which is a modern browser that supports HTML4 & doesn't support Javascript. But your guide should (imho) centrally focus on the common expectation of how popular browsers work.
Web browsers are extremely complex, requiring millions of lines of code in order to deal with a huge variety of Internet standards (and not just the basic ones such as HTML, JavaScript and CSS).
A while ago I wanted to see how much of this AI could get done autonomously (or with a human in the loop), you can see a ten-minute demo I posted a couple of days ago:
https://www.youtube.com/watch?v=4xdIMmrLMLo&t=42s
The source code for this is available here right now:
http://taonexus.com/publicfiles/jan2026/160toy-browser.py.tx...
It's only around 2,000 LOC so it doesn't have a lot of functionality, but it is able to make POST requests and can read some Wikipedia articles, for example. Try it out. It's very slow, unfortunately.
Let me know if you have anything you'd like to improve about it. There's also a feature requests page here: https://pollunit.com/en/polls/ahysed74t8gaktvqno100g
i can see a few reasons for slowness - you arent using multiprocessing or threading, you might have to rework your rendering for it though. You will need to have the renderer running in a loop, re-rendering when the stack changes, and the multiprocessing/thread loop adjusting the stack as their requests finish.
Second, id recommend taking a look at existing python dom processing modules, this will allow you to use existing code and extend it to fit with your browser, you wont have to deal with finding all the ridiculous parsing edgecases. This may also speed things up a bit.
Id also recommend trying to render broken sites (save a copy, break it, see what your browser does), for the sake of completion
EDIT: Unfortunately, it seems that the code is getting near the limit of the context window for Claude, so I'm not able to add several of the feature suggestions you added with the present approach. I'll look into breaking it up into multiple smaller files and see if I can do any better.
I'm wondering if examples with Browser/Server could benefit from a small visual, e.g. a desktop/laptop icon on one side and a server on the other.
Thank you! It is a good suggestion. Let me think about it.
The step I am missing is how other resources (images, style sheets, scripts) are being loaded based on the HTML/DOM. I find that crucial for understanding why images sometimes go missing or why pages sometimes appear without styling.
Thank you!
What's your next steps, do you plan to add more details of the reflow process?
Posts like this are the modern version of that.
i think the guy who created tailscale wrote about something like this...
Personally, I have my browser set up to "guess" as little as possible, never do the search from the URL bar unless explicitly told to do so using a dedicated search keyword (plus I still keep separated auto-collapsing search bar). I have disabled all guessing for TLDs, auto prepending www. In short, when I enter "whatever" into my URL bar, my browser tries to load to "http://whatever/", what could be my local domain and I could get an answer -- it is is a valid URL after all. In a related note, I strongly doubt that any browser does the web search for "localhost".
The rabbit hole could naturally go even deeper: for example most browser still interpret top-level dataURIs. It is not that long browsers interpreted top-level `javascript:` URIs entered into URL bar, now surviving in bookmarklets but taken from all users for the sake of a pitiful "self-XSS prevention".
So I would be really careful telling what happens -- or, god forbid, should happen -- when someone types something into their URL bar: "whatever" could be a search keyword with set meaning: - it could be bound to http URL (bookmark), - the bookmark URL could have a `%s` or `%S` and then it would do the substitution, - it could be a `javascript:…` bookmark ("bookmarklet"/"favelet"; yes, most browser still let you do that, yet alas, mostly fail to treat CSP in a way it would remain operational). - It could be a local domain.
The fact that, statistically, "most" browsers will do a web search using some default engine is probably correct but oversimplifying claim that glosses over quite a lot of interesting possibilities.