Svelte 5 bundle size news?

[frederikhors]

I've been impressed by the speed and performance of Svelte 5 from various posts I've read.

However, I'm concerned about its bundle size. Svelte 4's bundle size tends to grow significantly with additional components.

Can we expect improvements in this regard with Svelte 5? Are there any relevant posts discussing this?

We're about to embark on a project with numerous components, and while some team members advocate for Solid, I'm in favor of Svelte. Bundle size is a critical factor for us.

Thanks for your dedication and hard work.

[7nik]

The team mentioned it a few times quite a long ago: the minimal bundle size is bigger, but the further increase is smaller than 4.
E.g. in https://www.reddit.com/r/sveltejs/comments/18jdxht/i_have_migrated_147_components_to_svelte_5_and/ the author got the following result of migrating 147 components to Svelte 5:

The demo build file (JS) was with v4: 382kb - and with v5: 171kb (55% smaller)!

[ancashoria]

At first I was suspecting Vanilla Extract, but I have also removed all the styles and imports and the component is almost the same size.

[brunnerh]

Svelte has a runtime for its reactivity that needs to be included, so if you only have one or two components, this runtime will have a significant size compared to the user code. If you have a full application with a higher number of components, the size of the runtime will not be as significant any more.

[ancashoria]

I hear you, but I still find it sketchy (and I'm refering to my code here). I also added an embla carousel with the embla carousel svelte integration and that component landed at 80kb raw. When I added slightly more markup to it, it continued growing significantly.

I should mention I'm using Astro + Svelte integration.

At that point I decided I can't keep refactoring my components to Svelte as my page size would be huge.

[7nik]

Svelte 3/4 has just a few shared functions, while anything else (reactivity and updating DOM) is the generated code. As a result, the compiled components are bloated and the bundle size quickly became colossal on big projects. But, for the app with just a few very simple components, the minified bundle can be even below 1kb.
Svelte 5, practically, has the core (though it is tree-shakable) which is the minimal limit of the bundle, but the compiled components are compact, and thus further growth is quite moderate. So, a Svelte 5 app with at least dozens of components, will be around 1.5-2 times smaller than Svelte 3/4.

Also, you can use rollup-plugin-visualizer to analyze what your bundle contains and their sizes.

[ancashoria]

At this point I'm pretty sure Vanilla Extract is the problem

https://vanilla-extract.style/