I'd extend this to "web apps that revolve around forms, views, filters and pagination" when it comes to "Ajax" stuff (yes, I'm old).
The part of htmx that's relevant to these topics being discussed here, I once wrote an inferior clone of, some years ago.
It was "isomorphic", tailored to our PHP-based CMS, and could handle filters, search forms, and pagination.
Suitable for forums definitely, and current PHP-based forum software vendors that are still on the market follow the same paradigm.
I'd say that "Endless Scroll" is a good example of something that is... well maybe not interactive but still breaks the "just an HTML document" page metaphor that plays nice with such things.
Now, personally I find the UI compromises it takes to make endless scrolling happen are abhorrent (like not being able to ctrl-F or export the page content). But other people obviously like them.
Is that the kind of thing you'd be giving up as you move to a platform like HTMX?
Maintaining a code path with a snippet for each possible viewing experience, back when REST was all the rage, was a bit obnoxious though.
If you want basic interactivity, HTMX is fine.
If you want something more (like sortable) I'd reach for lit instead of adding the Sortable.js dependency, something the HTMX docs suggest ( https://htmx.org/examples/sortable/ )
And yes there are also some scenarios that you want to control the whole routing and rendering stuff, then go for Solid, React, Angular, Vue, whatever.
There is no golden rule to all of this but finding out what makes sense is a fun exercise.
But interactivity in largely content-driven sites doesn't necessarily preclude HTMX. You can do a bunch of fancy interactive stuff with HTMX and some minimal JS. Drag and drop sort is a tiny drop-in JS snippet. Skeleton loaders and spinners are supported out of the box in HTMX as is infinite scroll as others pointed out.
I'm not saying Next.js, Solid Start, Remix, Nuxt or some other hybrid server and client rendered model doesn't work for forum software. Or that even client only rendering can be a valid approach if you accept the trade-offs (no curl-ability). People should use whatever they feel productive building with.
But if your backend is already a non-JavaScript server rendered framework like Django then HTMX makes a ton of sense to add some interactivity.
Otherwise, I'd recommend HMTX even if you have a super flexible JS backend.
That said, this is all baseless thinking without seeing any requirements and as I said before, trying to choose the right abstraction is the hard but fun part.
"Fun" as in you're years into a project before you fully accept that you made the bad call.
I get lazy-loading for pages that contain a ton of media of which the user will likely only see a fraction. But some people seem to think infinite scroll is a good idea with text based content as well..
That's how interactivity has always worked.
Server-side render everything + ship interactivity via js on top of it.
I feel like most of the web developers forgot that React/Vue/etc solve a specific problem: single-page application.
This is a very narrow and specific problem: navigating from page to page not causing full page reloads.
But the web has changed since SPAs were needed in major ways:
1. the average device and connection is insanely faster than 10-15 years ago. Receiving and rendering content is not the problem it once was in the age of 2g connections and limited hardware mobile devices. Even the very low end phone from few years ago has nowadays 0 problems loading and parsing few hundred kbs of html and js.
2. Web technologies moved at all levels. Server technologies, cloud ones, browser ones. React and company are solving problems that barely belong to the modern web.
In short: today you can have an app-like, spa-like experience even out of fully server-side rendered applications. While also benefitting from shipping much less code to the client.
There's a very minimal amount of websites and applications out there that benefit, and aren't crippled by these rendering libraries: those that vastly leverage offline capabilities of the platform and want to keep working regardless of internet being available. I'm talking the notions and linears.
But bar from those, still working with this React slop is just not good for the user. Even multi billion companies hiring leetcode ninjas can't get acceptable user experience and performance out of those libraries, and it's not a coincidence: they keep forcing the wrong tool for the wrong problem.
They keep living in 2018 and at the end of the day the only excuse for those react/angular+tailwind slop is that there's an entire generation of developers that doesn't know anything else and has long lost any proper engineering skill (if there is any) in finding the right tool for the problem. This is a familiarity issue, not sound technical decisions. It's the "you can't go wrong with oracle/mysql/ibm", but actually you can, and it shows.
What's worse: it's incredibly cheap to experiment different solutions and approaches via LLMs in 2026, but people keep slopping the same monstrosities.
Using the same reasoning, I’d come to the opposite conclusion. Devices are much faster than they were 10-15 years ago, but network latency is still roughly the same because physics limits how much it can improve. So reducing network round trips matters more than ever, which favors SPAs over MPAs.
SPA’s tend to require more network round trips, sometimes significantly more based on the architecture.
The UX for an SPA can indeed be excellent, but the average SPA is worse than the average MPA, in my opinion. It’s just much easier to break things in many subtle ways in an SPA.
The creator of HTMX would disagree with you (as the person who described and coined the term REST)
https://htmx.org/essays/how-did-rest-come-to-mean-the-opposi...
That's not true. They solve the problem of requiring separate code paths for interactive elements - one for initial render and another for updates.
Previously the server rendered the initial HTML and then client JS updated it after e.g. user clicks a button, but with React/Vue/etc., it's merged into one code path because HTML is derived from the current state.
> Even multi billion companies hiring leetcode ninjas can't get acceptable user experience
Modern UX is bad because many front-end programmers fundamentally just do not care about the UX, it's not about the specific tech they use.
This is untrue and is weird misunderstanding on your part. Most of modern UX and UI is designed to fit the needs of the customer for the frontend team/dev: the product or marketing or sales department. The user of the website is very rarely the customer for the dev.
That's the definition, I didn't made it up.
And those libraries solve that.
Your other definition, can be fully implemented server side, Elixir's Phoenix does that. But it's not the only one.
Your prior claim was that they only solve one problem, not about a definition. They solve several problems:
- less data can move over the wire compared to sending a full page every time (this is in your definition, and is definitely not always true, as sometimes REST APIs can return far more data than what's needed to render the screen)
- the same REST/data API can serve your website and other consumers, e.g. any native mobile apps or third party API consumers
- you can write tests for your frontend, e.g. you can unit test components' behaviour and style in isolation
- the frontend can also work, or at least respond usefully to the user, when the network or the backend are not working
In a reasonably complex application, each interface ends up needing its own shape of optimized APIs. Otherwise the clients become very complex munging/reshaping data or making too many API calls, throwing away a lot of data etc.
According to what you said, CSS also solves the problem of making an SPA because you could "switch pages" by changing CSS class names on `body`. But if someone asked what CSS is you're not gonna answer "you use CSS to make an SPA", even though _technically_ you can use it to make an SPA.