52 replies
23h59m
the longest post on my site, takes 92 KiB instead of 37 KiB. This amounts to an unnecessary 2.5x increase in load time
Sure, if you ignore latency. In reality it's an unnecessary 0.001% increase in load time because that size increase isn't enough to matter vs the round trip time. And the time you save transmitting 55 fewer KiB is probably less than the time lost to decompression. :p
While fun, I would expect this specific scenario to actually be worse for the user experience not better. Speed will be a complete wash and compatibility will be worse.
Well, that, and there's an 850K Symbols-2048-em%20Nerd%20Font%20Complete.woff2 file that sort of drowns out the difference, at least if it's not in cache.
Now I got curious, and there's also a 400 kB CSS file to go with it: https://purplesyringa.moe/fonts/webfont.css
I'm not up to date on web/font development – does anybody know what that does?
It adds unicode characters before elements with the given class. Then it's up to the font to display those Unicode characters — in this case, based on the class names, one can infer that the font assigns an icon to each character used.
That makes sense, thank you!
So the purpose is effectively to have human-readable CSS class names to refer to given glyphs in the font, rather than having stray private use Unicode characters in the HTML?
Yep
This is a reasonable approach if you have a large number of icons across large parts of the site, but you should always compile the CSS/icon set down to only those used.
If only a few icons, and the icons are small, then inlining the SVG is a better option. But if you have too many SVGs directly embedded on the site, the page size itself will suffer.
As always with website optimization, whether something is a good option always “depends”.
More reasonable than this class+CSS would be e.g. a React/static-website-template/etc custom element that outputs the correct glyph. The output doesn't need to contain this indirection, and all of the possibilities.
I think at least some recent tools will produce ligatures to turn a plain text into an icon to avoid this issue.
Another detail is that this feature breaks and makes some sites nearly unusable if the browser is set to ignore a website's custom fonts.
seriously, why can't modern browsers turn off features like remote fonts, webrtc, etc. in settings. I hate when reading a bit then the font changes. Not to say fingerprinting risks.
You can, and then when someone uses an icon font instead of graphics their page breaks.
Skill issue.
Pictures are pictures, text is text. <img> tag exists for a reason.
Its a convenience packaging issue. An icon font is simply more convenient to handle. <img> tags for a hundred images requires more work.
Icon fonts are used all over the place - look at the terminal nowadays. Most TUI's require an icon font to be installed.
So it's a skill issue.
I believe many Web APIs can be enabled/disabled on a website basis, no?
iPhone lock down mode turns off remote fonts (including breaking font icons as sibling says)
Wow, yeah. That kind of discredits the blog author a bit.
It's cached. Not ideal, sure, and I'll get rid of that bloat someday, but that file is not mission-critical and the cost is amortized between visits. I admit my fault though.
Definitely fair and I was a bit harsh. It just seemed a bit nonsensical to go through such efforts to get rid of a few kilobytes while serving a massive font file. But I also understand that it's mostly for fun :)
I mean, it's all just for fun of course.
That size difference is large enough to make a difference in the number of round trips required (should be roughly one fewer roundtrip with any sensible modern value for the initial congestion window).
Won't be a 2.5x difference, but also not 0.001%.
You don't need a new roundtrip for every packet. That would be devastating for throughput. One vs two vs three file packets get acked as a batch either way, not serially.
Also when you get to the end, you then see
At 69 KiB you're still over the default TCP packet max, which means both cases transmit the same number of packets, one just has a bunch of extra overhead added for the extra JavaScript fetch, load, and execute.
The time saved here is going to be negligible at best anyway, but there looks to be actually negative because we're burning time without reducing the number of needed packets at all.
Those numbers are for a different page. For the original page, the article quotes 44 kB with this method vs. 92 kB for gzip.
What? No, they absolutely don't transmit the same number of packets. Did you mean some other word?
I expect what GP meant is the default TCP window size, so in a situation where bandwidth costs are dwarfed by roundtrip costs, these two cases will end up taking essentially the same time, because they will incur the same number of ACK roundtrips. Don’t know if the numbers work out, but they at least sound plausible.
No, there is no way the numbers would work out to the same number of roundtrips. The sizes are different by a factor of 2.5x, and the congestion window will only double in a single roundtrip. The only way the number of roundtrips would be the same is if both transfers fit in the initial congestion window.
Yes, sorry
They were probably thinking of the max size for packets in TCP, which is 64K (65535 bytes).
However, Ethernet has a MTU (Maximum Transmission Unit) of 1500 bytes. Unless jumbo frames are used.
And so I agree with you, the number of packets that will be sent for 69 KiB vs 92 KiB will likely be different.
Interesting, how does that add a round trip? For the record here's what I believe to be the common definition of an additional "round trip", in a web development context:
So you're starting a new request that depends on the client having received the first one. (although upon closer inspection I think the technique described in the blog post manages to fit everything into the first response, so I'm not sure how relevant this is)In reality it's more like:
It's all about TCP congestion control here. There are dozens of algorithms used to handle it, but in pretty much all cases you want to have some kind of slow buildup in order to avoid completely swamping a slower connection and having all but the first few of your packets getting dropped.Doesn’t client see reference to Y at this point? Modern browsers start parsing HTML even before they receive the whole document.
Not just modern. This was even more significant on slow connections, so they've kind of always done that. One could even argue that HTML, HTTP (specifically, chunked encoding) and gzip are all intentionally designed to enable this.
Unless a resource is very small, it won't be transmitted in a single atomic unit. The sender will only send a part of it, wait the client to acknowledge having received them, and only then send more. That requires a network roundtrip. The larger the resource, the more network roundtrips will be required.
If you want to learn more, pretty much any resource on TCP should explain this stuff. Here's something I wrote years ago, the background section should be pretty applicable: https://www.snellman.net/blog/archive/2017-08-19-slow-ps4-do...
That's certainly reasonable if you optimize only for loading time (and make certain assumptions about everybody's available data rate), but sometimes I really wish website (and more commonly app) authors wouldn't make that speed/data tradeoff so freely on my behalf, for me to find out after they've already pushed that extra data over my metered connection.
The tragedy here is that while some people, such as the author of TFA, go to great lengths to get from about 100 to 50 kB, others don't think twice to send me literally tens of megabytes of images, when I just want to know when a restaurant is open – on roaming data.
Resource awareness exists, but it's unfortunately very unevenly distributed.
We need a MoSh-based browser with gopher support.
and you'd need AI to tell you whats in the pictures because lots of restaurant sites just have photos of their menu and some designer with no web knowledge put their phone number, address, and hours in an image designed in Photoshop
You're in for bad luck. Some time ago I tried some photos of pasta dishes with Gemini and it could not guess the recipe name.
I've found Gemini to be pretty terrible at vision tasks compared to the competition. Try GPT-4o or Claude-3.5-Sonnet instead.
There is an interesting "Save-Data" header to let a site know which makes sense to optimize for on connection but it seems to be Chrome only so far https://caniuse.com/?search=save-data
I wish there was a bit of an opposite option - a "don't lazy/partially load anything" for those of us on fiber watching images pop up as we scroll past them in the page that's been open for a minute.
Why is there more latency?
Edit: Ah, I see OP's code requests the webp separately. You can avoid the extra request if you write a self-extracting html/webp polyglot file, as is typically done in the demoscene.
It takes more time for your message to get back and forth between your computer and the server than it takes for the server to pump out some extra bits.
Even if you transmit the js stuff inline, the op's notion of time still just ignores the fact that it takes the caller time to even ask the server for the data in the first place, and at such small sizes that time swallows the time to transmit from the user's perspective.
Here's a demo that only uses a single request for the whole page load: https://retr0.id/stuff/bee_movie.webp.html
It is technically 2 requests, but the second one is a cache hit, in my testing.
That's fine, but if you're evaluating the amount of time it takes to load a webpage, you cannot ignore the time it takes for the client request to reach your server in the first place or for the client to then unpack the data. The time saved transmitting such a small number of bits will be a fraction of the time spent making that initial request anyway. That's all I'm saying.
OP is only looking at transmit size differences, which is both not the same as transmit time differences and also not what the user actually experiences when requesting the page.
Hmm? I'm not sure where you're taking that from. The webp is inlined.
Ah, so it is! I was skim-reading and stopped at `const result = await fetch("compressor/compressed.webp");`
Seriously, if you're saving less than a TCP receive window's worth of space it's not going to make any difference to latency.
I suppose it could make a difference on lossy networks, but I'm not sure.
If the blob contains requests (images, but also stylesheets, JS, or worst case fonts), it will actually instead be a net negative to latency. The browser's preload scanner begins fetching resources even before the HTML is finished being parsed. That can't happen if the HTML doesn't exist until after JS decodes it. In other words, the entire body has become a blocking resource.
These are similar conversations people have around hydration, by the by.
> These are similar conversations people have around hydration
For the uninitiated: https://en.m.wikipedia.org/wiki/Hydration_(web_development)
Actually, I was rather wondering about that claim, because it seems accidentally cherry-picked. Regarding that post:
But regarding the current one:
Most of the other examples don't show dramatic (like more than factor-of-2) differences between the compression methods either. In my own local testing (on Python wheel data, which should be mostly Python source code, thus text that's full of common identifiers and keywords) I find that XZ typically outperforms gzip by about 25%, while Brotli doesn't do any better than XZ.
XZ was never considered to become a compression algorithm built into web browsers to start with. Brotli decoder is already there for HTTP, so it has been proposed to include the full Brotli decoder and decoder API as it shouldn't take too much effort to add an encoder and expose them.
Also, XZ (or LZMA/LZMA2 in general) produces a smaller compressed data than Brotli with lots of free time, but is much slower than Brotli when targetting the same compression ratio. This is because LZMA/LZMA2 uses an adaptive range coder and multiple code distribution contexts, both highly contribute to the slowness when higher compression ratios are requested. Brotli only has the latter and its coding is just a bitwise Huffman coder.
It’s not just decompression time. They need to download the whole thing before decompression, whereas the browser can decompress and render HTML as it’s streamed from the server. If the connection is interrupted you lose everything, instead of being able to read the part you’ve downloaded.
So, for any reasonable connection the difference doesn’t matter; for actually gruesomely slow/unreliable connections where 50KB matters this is markedly worse. While a fun experiment, please don’t do it on your site.
Other major issues that I had to contend with:
1: browsers choose when to download files and run JavaScript. It is not as easy as one might think to force JavaScript to run immediately as high priority (which it needs to be when it is on critical path to painting).
2: you lose certain browser optimisations where normally many things are done in parallel. Instead you are introducing delays into critical path and those delays might not be worth the "gain".
3: Browsers do great things to start requesting files in parallel as files are detected with HTML/CSS. Removing that feature can be a poor tradeoff.
There are a few other unobvious downsides. I would never deploy anything like that to a production site without serious engineering effort to measure the costs and benefits.
I have similar feelings on js minification especially if you're sending via gzip.
exactly what I thought too