In Arial, they're indistinguishable. In Roboto, you can see the difference if they're right next to each other (l is longer than I). Segoe UI has different variants but the one I've found on the MS web site has very similar or identical lI's, just like San Francsico.

I know, fixed width fonts would fix that, but not everything that should will be in those. And especially on a programming website, that matters.

Reason being that in general text we don't read based on individual letters, we recognize "shapes" of words.

That's because it deosn’t mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.

    Your Passcode is: 6234024

It's pretty noticeable with the monospace font that used on my system because O is more like a circle and 0 is thinner. There is no slash, and it is fortunate because it could be mistaken with Ø otherwise.

Another option, like on my system, is that zeros have a dot in the middle.

Is it actually a zero or am I missing something?

It's even more prescient considering that on my screen, those two letters look exactly the same.

https://fonts.google.com/?preview.text=l%20I&preview.text_ty...

How is it good with the pipe? I l | 1

edit: very good. It is also good for 0, O and Ø. It is also very readable. A very good font.

Noto Mono is used for monospace, it has the same qualities. I really recommend this set of fonts.

With JuliaMono for programming I’m finally happy with fonts everywhere :).

IMO custom fonts are fine (beneficial sometimes, matching fonts used in any relevant logos and so forth) for titles and other big text, but for body text stick with something basic and/or familiar to the user.

Also, Helvetica clones exist mainly to get around licencing costs related to physical printers (if your software uses something metrically identical you can just use the existing postscript drivers). SF and Segoe are for UI text, which Helvetica is not suited to (Apple had to adjust the metrics to make it more usable, for example)

I'd say a custom font isn't important for any site. Except perhaps a font fountry showcasing their wares.

I do wish OS and/or browser vendors added more agreed system fonts though (pre-installed and ready to go). So that we have a selection of say 100 fonts guaranteed to be on Windows, macOS, Linux, iOS, Android, FreeBSD... I guess adding emojis anually is more important...

I also believe performance should trump other design aspects of a website. This means including using the default Operating System (OS) font stack over a custom font if it means faster page loads.

However, I also recognise that a carefully chosen custom font plays a big part in the aesthetics of a website. It can set the tone of the website as well as giving it a distinctive look that sets it apart from other websites. Can you imagine books, posters, magazines, films etc all set in a limited palette of available fonts? The variety of typefaces available is infinite and the printed word is immeasurably richer for it.

There are ways of limiting the download size of fonts. For example, limiting typeface weights (e.g. 3 weights only: regular, bold, italic) can amount to approx 60kb of downloads in total (20kb per font x 3 using the WOFF2 font format). That might still be too much for many developers, but I suspect that images will be larger (and possibly JavaScript too).

Print media just doesn't have any downsides to custom fonts so there's no reason to not use them.

But there is one where it did matter: the Nigerian Oil Spill Monitor [1], a data entry and exploration application I built in 2013-2019.

I did try different free fonts, and found that with Ubuntu I could read the data much more accurately so I put it there as a webfont even if I was trying to minimize the amount of data loaded. (Internet bandwidth in Nigeria was not great at the time; many of our users used the application through shared GSM links.) Maybe by now, with the application’s users having better screens and improved font rendering, it would be fine to remove the Ubuntu font. Back then, with fewer pixels, it was the best way to pack information in the screen.

[1] https://sentido-labs.com/en/portfolio/#Nigerian-Oil-Spill-Mo...

However the Droid Serif font that ships with Android isn’t boring — it’s just awkward. Blockier than Times New Roman, with serifs that jut out. Reading a page of text in it does make me notice the font — and not in a good way.