I couldn't agree more. BTW, 98% of US users have JavaScript enabled in 2025.

https://www.mediawiki.org/wiki/No-JavaScript_notes

This concept is missed so much in AI research and is quite frustrating.

Reminds me of the Meat Loaf song “Two Out of Three Ain’t Bad” which was released in Japan as 66%の誘惑 “66% is Good Enough” https://www.discogs.com/release/8303076

I wonder how much traffic from bots is skewing OPs nested CSS calculations

That reminds me of an old comic where a guy picks a milk carton from the grocery store shelf and reads in the box: "Now with 0.01% less semen." and he does not know if he's happy or sad about it.

I agree the general premise but do not agree when it comes to browser support.

I feel like we should be building for the 98% or even 95% and force the remaining to upgrade their browsers. I've built for the IE6 - IE11 era for a painful and long time. I do not give a shit if you want to use a 3 year old browser at this point. Go look at a blank screen.

Depends on the context

Pragmatically, often users without new browsers and OSses are not the best clients. In ideal world, sure, I want to support everyone. In a world with limited resources, I would better spend my time elsewhere.

If it's uptime it's definitively not much!

1% failure rate of a hundred might be acceptable. 1% failure rate of a million is not.

Isn't that a named law?

This applies to AI too.

Your classifier might be 98% accurate and it may sound like a lot.

But if it sits inside a car, making thousands of decisions during every trip then you may be in deep trouble.

The author seems to equivocate by comparing completely different domains.

Whether 98% is acceptable, it depends on the cost of failure, not the percentage itself.

while true, the people who will read this and then think twice about implementing and applying things are exactly the people who already doing too much thinking

I am not exactly sure what is the article trying to point out

> Truly robust engineering isn’t about what works for most; it’s about gracefully handling the edge cases.

How do you justify this when you factor in cost and time?

I think this single fact is a major source of enshittification in large software products, especially in the era of ML/AI. If your quality is 99%, it sounds like "you have solved your task", but in reality there is a long tail that over time affects nearly every customer.

I've seen this so many times. 99% of search results are good (so within 100 queries you'll hit at least one bad result with p≈0.63), 99% of dashboard panes load normally (so a dashboard with 20 panes is broken in nearly 1 in 5 loads), and so on. If your LLM gets 99% of tool calls right, nearly every session will contain a malformed tool call.

Probabilities are hard for humans, probably.

> Can you imagine a venue refusing entry to former clients 2% of the time just because they’ve “improved their experience”?

This reminds me almost precisely of the dynamics of pro sports in the US and how fans are getting priced out of attending games or even watching teams on TV as organizations shift to bespoke streaming platforms.

It's just mathematical expectation.

Don't look at the simple probability - look at probability * value.

Alternatively, 98% is plenty.

If your business plan requires you to capitalize on more than 98% of the market, it's already a failure. It'll never happen.

As always, it's an "it depends" situation. If your userbase is largely luddites, then maybe you need to support 10+ year old browsers that can't be updated. Otherwise, you can probably just worry about people who are using computers new enough to actually update their browser once a year or better.

The tradeoff is code complexity and engineering time, vs having a larger market. And that's going to be an individual situation for every company.

There's likely always a line somewhere where effort becomes way out of proportion compared to getting that last mile effort.

Arguably, if you only have a website, that won't work for anyone without access to the Internet. So then you should have a physical presence in each of those people's location, and arguably you shouldn't provide any improvements that give me more than physical presence does, so you should not have the website in the first place, since people without the Internet can't use it or you have to keep your website without any improvements over the physical office.

If you only have a website, arguably 2+ billion people currently wouldn't be able to access it.

And it seems odd to bring 150 mil people as an example, when the baseline should be at least 2+ billion with website only.

What about those 30% of audience to update their browser? On our web platform, the team currently displays a message along the lines of: 'Please update your browser; this site relies on features incompatible with your current version'.

Isn't this obvious?

In some categories, certainty and percentages make a lot of difference--surgeries, accidents. In some, they don't--surveys, grades.

It just depends on the category.

This is akin to saying something as obvious as more percentages are more than less percentages.

While I agree with the general sentiment, the problem here isn't developers not being familiar with statistics, it's the simple fact all of this is profit driven most of the time.

I tried to purchase tickets for an event last week. I had to go through Ticketmaster as it was the only official way. They forced me to verify my account using a phone number, but whoever they were using for messages wasn't able to deliver a code to my number. I tried a few numbers from our household and they all failed.

Searching for this issue yielded a bunch of results, so it was definitely a known issue, but there wasn't anything I could do, really. To them, it's simple math. Another SMS provider that covers my (tiny EU) country might be more expensive. They might be avoiding scammers that used my mobile operator in the past. Whatever it is, it would probably cost them more than they lose in ticket sales.

Without some government entity to force them, they don't give a shit about me being able to see an event.

Nice in theory, in practice I remember having to support Internet Explorer about 4 years ago. Hard to justify the investment sometimes, at least polyfills gave use some sanity back. The only reason to do it was: Rich old enterprise customer who can't install chrome due to policies created by Dinosaurs.

Websites are surprisingly hard to maintain long term, specially for a broad audience of devices. Developer Experience can lead to better UX, the easier it is to build/maintain, the more likely we're to do it.

Given how bad AI is at design plus all the unstoppable slop train, I expect websites to become much, much worse.

Covering for the 2% is often not a sound first order business decision. There's certainly higher order benefits. A lot of accessibility features are just plain useful for anyone. And I think companies like Apple generally get that it's a kind of loss leader. But this article makes dishonest TV Shopping Network style arguments like pointing at 150 million as if that was ever an addressable market.

I think either you argue for regulation, or you argue more honestly: asserting that the extra cost will likely never directly pay for itself, but it is some of the secret sauce that can a good product into a great one.

I usually go by CanIUse's global percentage when deciding if I can utilize a new browser feature, and right now it's 90.81% (https://caniuse.com/css-nesting)

That's a bit lower than I would be comfortable with, however not that bad, we have been even considering switching all our images to AVIF: https://caniuse.com/?search=AVIF

And google uses Webp all over the place and that's sitting at 96% https://caniuse.com/webp

Author's 98% take is a bit misguided.

We shouldn't go out of our way to support IE11 anymore, sorry

Relavent XKCD comic: https://xkcd.com/325/

Hover text: You can do this one in every 30 times and still have 97% positive feedback.

I blame it in big part on the WebDX community group, their absolutely useless "Baseline" guidelines, and on them allowing Apple to be part of that group and make decisions on what features are "ready" to use whilst being behind the only non-evergreen browser in 2026.

The "baseline" means nothing. The percentage in caniuse means nothing. The only number that matters is the number of Safari users stuck using a no longer supported Apple device that access your website. Of course Apple makes sure to hide usage stats of older devices.

Everyone complains about only having three browser engines out there, but I'll be happy to go down to two if that means freeing the world from Safari.

I was heading to dinner with a friend who worked in infra. Google maps said we could bike across town in 20 minutes. He suggested we leave 40 minutes ahead of time and grab a drink at the bar if we got there early. When I raised an eyebrow, he goes:

"What, do you not live your life based on 99th percentiles?"

I tend to think of work as upside-based on downside-based. Most feature work is upside. 10% lift on conversions is great, 40% adoption is winning, and you're playing for the moonshot of 10x. Infra work is downside-based. 98% secure, 98% available, 98% acceptable performance -- that'll all failure. Winning means the thing works as expected and nobody notices.

Not everything sorts cleanly into upside vs. downside, but a lot does. Allocate your risk accordingly.

>> But a restaurant where clients don’t get of food poisoning 98% of time is getting people sick on a monthly (or even weekly) basis.

Objectively, I think it's impossible to work in the food industry and avoid food poisoning 100% of the time. One of the reasons I never attempted several of my food industry business ideas. I'm certain they would be at least profitable enough to keep going, would be rather trivial to access EU subsidy money in the €50k, but the amount of regulations and inspections terrifies me. And I'm sure at some point, some salmonella or what else would slip through and don't wanna deal with the consequences.

Easier with programming computers since a "bug" won't make people expell waste simultaneously through both incoming and outgoing food orifices, like it happend to me last time I ordered sarmale from a local restaurant. Like in the food industry a "bug" is literally that.

Off topic (and at risk of being downvoted), I don't think I'll ever get a better chance to insist here that

"99 and a half won't do"

https://youtu.be/1QVJCjbgM-s

Holy Disciples

Trying to Make a Hundred

This whole article is a categorical error. Whether something is good or not entirely depends on the frame of reference and the context. You can argue endlessly by shifting the topic that 98% is used on. I guess that's what people are doing here.

There are cases when providing service for remaining 2% isn't profitable. It's better just say "sorry".

I used to work in company where we have spent a lot of time making custom fixes for our software in order to work-around wired hardware/software bugs on machines of individual customers. Yes, we provided service for remaining 2% or so, but in cost of slowing-down overall product development and not making our product better for remaining 98%.

This analogy is bad: Nobody is going to die or get food poisoning because their old browser doesn't work on a website.

A better analogy would be a restaurant deciding not to cater to the 1% of the US population that have celiac disease (cannot eat gluten), or the 2% that have issues with dairy.

But is it? Addressing 98%of TAM, is?

Suppose 98% users have not had any sessions crash. You want to build an addon feature that 10% of your users will buy and which will increase the revenue from those users by 30%.

Do you spend time building the feature, or trying to understand why 2% of users sometimes see crashes?

Reminds me of statistic where most customers already stop going to a particular supermarket if it stops carrying a handful of the items they want to buy

It may sound like a small deal to not carry one brand of chocolate paste but if some customers then also don't buy the 12 other groceries they need at your shop, it doesn't really matter that it's only 2% of products that were discontinued. Supermarket products are so stable not because nobody ever makes anything new but because changing a small percentage frustrates customers

If I can't order from some website, I stop trying. Maybe next week the ESR browser gets an update and it works again but by then I'm not clicking those links in the search results

I like to think it depends on what the actual topic is. Even the article's examples reinforce this.

98% market share? Amazing. 98% browser support? There are 15 billion screens in the world. 2% of that is 300 million. Hardly a number we can ignore. Edge cases for those 2% should be considered and implemented

Software isn't the product though.

Just like the article says, it depends on if the product is an essential or a dessert.

If your product is a "essential necessity" one, then 98% is terrible for your software.

If your product is a "dessert", then for it's software 98% is awesome.

In today's world of AI it's fairly easy to make your site compatible with every version of internet explorer ever.

Just tell the AI to do it. It'll find a way. The maintenance burden for you will be minimal because the AI can keep the legacy compatibility bits in sync.

If for 2% of users a webpage will not look as awesome as intended (it's not guaranteed that it will be broken), that's ok. It's not poisoning - it's a 98% chance of getting a top mark.

And the last 2% is often the hardest part. The low-hanging fruit has been picked, so you're left with these tricky edge cases that may not have a straightforward solution.

> If a website uses fancy new browser features and works for 98% of the population, that means that it won’t work for ~150 million people.

Yes, because all of us have website serving, checks notes, the entire world...

98% is probably in the neighborhood of 8% more than I'd require for browsers compatibility before deciding to use a new feature. At a certain people need to update and we do ourselves and our other 98% of customers no favors by catering to the lowest common denominator.

See also, the story of YouTube adding a banner pushing people to upgrade off old IE version being a large factor in people upgrading. Now, obviously, we aren't all running YouTube-sized sites but building for ancient browsers is, very often, a large waste of time.

In the age of evergreen browsers you have to go out of your way to be using something that's not at most a couple years out of date.

60% of the time, it works every time

Design bloggers are about to reinvent the concept of availability https://en.wikipedia.org/wiki/High_availability#Percentage_c...

Software standards are way too low these days. If you can't do at least 5 9s in everything you ship get out of the industry and humanity will be better off.

The close-to-home example that came to my mind while reading this is GPU programming, where the percentage multiplies. Maybe there are other similar examples where a large sounding percent needs an exponent and shrinks?

With CUDA you try to keep all threads doing the same thing. Sometimes that’s very difficult, but if each thread does the same thing 98% of the time, is that enough? Well since there are warps of 32 connected threads, you might expect the probability that any thread in the warp diverges to be .98^32, or 50% of the time spent with one thread in the diverged code. 50% still doesn’t sound that bad unless threads diverge at different times, and then 50% warp divergence might mean a 16x slowdown overall. 98% isn’t enough in this case.