Solidjs Creator On Fine-grained Reactivity As Next Frontier

Solid plans to present a caller primitive to its reactive architecture, according to a talk by SolidJS creator Ryan Carniato at JSNation past week.

There are 2 reasons why this matters: First, Carnatio, a leader successful nan model space, is demonstrating what he sees arsenic nan early for each JavaScript frameworks successful position of expanding their capabilities; and second, arsenic Solid goes, others sometimes follow, arsenic we saw pinch Signals adoption successful Angular and Preact.

Carniato explained signals arsenic “like a spreadsheet,” wherever a normal duty represents a infinitesimal successful time.

“It intends that connected completion, adaptable A reflects nan existent sum, but if either B aliases C changes, you person to do nan duty again.” he said.

Signals are conscionable a group of primitives to thief correspond nan synchronization, he added. Signals had been astir for nan amended portion of a decade erstwhile he open-sourced Solid.js backmost successful 2018, but Signals had fallen retired of favour acknowledgment to nan React Component Model, he said.

“It’s difficult to disregard nan effect erstwhile beautiful overmuch each model different than React has adopted Signals first-class astatine this point. So great, right? End of story,” he said. “No, I deliberation this: We’re conscionable astatine nan opening of a overmuch bigger change, and I’m not unsocial successful this thinking.”

He’s not talking astir artificial intelligence, either, but alternatively nan low-level architecture problem of getting nan astir retired of your applications.

“Just having Signals aren’t enough. Signals are a system for change, but really you usage them makes each nan difference,” he said.

The communal thread successful what makes Signals powerful is nan knowledge of nan information chart that powers your application, he said. It enables developers to do “incredible things that we wouldn’t easy beryllium capable to do otherwise,” he added.

He explored what Signals empowers successful nan talk, introducing codification examples that reference upcoming features of Solid that whitethorn not moreover been disposable astatine this time. That included a caller primitive connection for nan framework.

Signals Does Not Equal Faster Performance

Carniato began pinch a look astatine performance, because it’s nan easiest to talk astir and “arguably nan slightest important,” he said.

“This starts pinch debunking a communal misconception: I’m utilizing Signals truthful my App model must beryllium faster,” he said. “Unfortunately, it doesn’t activity that measurement arsenic Joe Savona from nan React squad recovered retired — if you watched his talk from React Conf 2025, wherever he showed that adding immoderate authorities guidance really lowers nan capacity ceiling of your framework.”

Carniato added that while nan React compiler mightiness let developers to constitute much optimal code, it doesn’t person a meaningful effect connected nan absolute performance.

Adding MobX, Zustand aliases Signals to React aliases moreover Signals to Preact isn’t guaranteed to amended nan capacity successful each cases, he explained. In fact, connected average, it makes them slower. That’s because frameworks are built astir nan Virtual DOM (VDOM) and each clip authorities updates, nan model has to rerun constituent functions and diff nan VDOM tree, which compares nan aged virtual character to nan caller virtual character to find changes.

The reply to Signals and amended capacity is recovered successful fine-grained rendering, he said. To that end, SolidJS eliminates nan VDOM and uses nan reactive chart to only update nan exact, fine-grained DOM nodes that dangle connected changed data. Solid arsenic good arsenic Svelte and Vue person joined Solid successful having a fine-grained rendering tree.

“Picture immoderate exertion wherever you request to propulsion authorities up precocious truthful it’s disposable astatine aggregate points, for illustration a shopping cart successful nan header and possibly a bargain fastener heavy successful your page,” he said. “You update nan state, you trigger re-renders down nan tree, only nan shopping cart really needs to update, but we do each of this other work.”

“This starts pinch debunking a communal misconception: I’m utilizing Signals truthful my App model must beryllium faster.”
– Ryan Carniato, creator of SolidJS

Typically, developers are told to memoize, which is caching nan consequence of a usability telephone and returning nan cached consequence erstwhile nan aforesaid inputs hap again, alternatively of recalculating nan result.

SolidJS, Vue and Svelte usage reactive primitives specified arsenic Signals that are fundamentally memoized. But memoization creates a trade-off betwixt velocity and memory.

“You tin recognize that nan information you nonstop down to nan bargain fastener isn’t changing, and only tally nan 1 path. Generally, this is what nan React compiler does. It’s what Svelte 3 did,” he said. “If nan cart has changed, there’s nary avoiding this: re-running each nan components, from nan proprietor of nan authorities down to that change. We tin prune branches that didn’t alteration on nan way, but nan alteration has to scope its spot successful nan UI.”

The constituent successful which you usage Signals enters nan character and becomes a caller route, he said.

“However, pinch fine-grain rendering, each props conscionable activity that way,” he said. “By default you tin state this information successful nan apical your app bottom, walk it done 10 components to nan nonstop aforesaid results. It doesn’t request to rerun nan full constituent aliases immoderate of its parents, conscionable nan parts change.”

That leads to nan full class of “will my constituent rerun” going distant and capacity creation becomes a non-issue, he said.

Svelte and Vue person joined Solid connected nan fine-grained rendering train, he said.

New Primitive for Solid

Stores are proxies wherever each spot has nan imaginable of being its ain Signal. Working pinch Stores led to Carniato realizing location are problems that require driving granular information and places wherever you commencement from a azygous root but want to fork aliases divided reactivity.

“It’s a discarded to cheque each statement erstwhile you’re changing nan selected people connected a table, but it isn’t ever applicable to see an ‘is selected’ connected each row, particularly erstwhile that information is shared successful aggregate places,” he said. “Sometimes we conscionable request to task reactive information onto different information without mutating nan source. Sometimes, we request to beryllium capable to create ephemeral extensions of that information for illustration merge and optimistic changes without committing them.”

He explained 2 precocious concepts successful SolidJS’s reactivity model, some aimed astatine eliminating nan request for analyzable broadside effects (like useEffect successful React) to negociate authorities synchronization.

The first is Projections, which would beryllium a caller primitive for Solid. It’s still successful nan works. Projections explicate and divided reactivity backmost into aggregate different sources, Carniato explained. They’re for illustration a specialized select aliases lens you spot complete nan main data. They are granular, derived and non-mutating. They besides fto developers create ephemeral changes for illustration an Optimistic UI update (showing nan users their alteration instantly earlier nan server really confirms it) without changing nan halfway exertion data, he explained.

“While you whitethorn not usage them very often, they correspond a abstraction that we’ve ne'er really had a bully solution earlier successful beforehand of frameworks — a primitive that is some granular and derived,” he said.

The 2nd is Async Signals, which are already portion of SolidJs implemented pinch createResource. Async signals are a solution for integrating slow information straight into nan fast, synchronous UI travel based connected reads.

“While you whitethorn not usage them very often, they correspond a abstraction that we’ve ne'er really had a bully solution earlier successful beforehand of frameworks — a primitive that is some granular and derived.”
– Carniato

Traditional models are write-centric, meaning you person to manually show nan model to update aft nan slow information arrives, often starring to analyzable logic wrong useEffect aliases lifecycle methods. But Solid’s attack is read-centric, truthful it should only region erstwhile it doesn’t person nan information to render (a “read” problem).

”What mightiness beryllium absorbing to you is because we’re fine-grained and because we tin push nan reactivity to wherever nan Read is,” he said. “Basically, children go siblings automatically successful this model.”

He past demoed really accelerated nan fine-grained reactivity attack loads: It took nan full page 2 seconds to load because they each tally successful parallel, he noted.

He besides discussed really this tin beryllium utilized to create “self-healing Reactivity” wherein nan reactive chart knows each dependencies, allowing nan model to automatically trace errors backmost to nan async root and retry nan fetch erstwhile a “Reset” fastener is clicked—without re-running nan constituent functions.

While fine-grained reactivity guarantees speed, nan exertion still faces a consistency problem known arsenic tearing erstwhile dealing pinch non-urgent, asynchronous updates. Carniato noted that SolidJS really tears by default aft first load — for instance, a antagonistic number mightiness update instantly, but nan accompanying slow-fetched building concisely shows nan aged data.

To lick this, SolidJS uses Transitions, which allows nan developer to people an update arsenic non-urgent. This primitive is basal for enabling nan smooth, concurrent rendering of asynchronous data. Transitions besides “can necktie together mutation and async fetching to region weird title conditions astir your information and pending states,” Carniato explained. Transitions tin beryllium utilized to guarantee an app doesn’t suffer from ocular “tearing” during slow information changes.

He noted that Solid has had these features since astir 2020, giving it acquisition pinch nan primitive. Transitions are a cardinal system for building a afloat functional Optimistic UI.

But nan champion is still to travel arsenic frameworks thin into fine-grained reactivity.

“I deliberation we’re astatine conscionable nan precipice of nan adjacent large thing,” Carniato told audiences.

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