Local-first sync engines have quietly become one of the more consequential infrastructure decisions a web team can make in 2026. Not because the pitch is new — "local reads and writes that feel instant, synced in the background" has been the local-first dream since the Ink & Switch essay popularized it years ago — but because the field of tools claiming to deliver it has matured enough to be a real, load-bearing choice, and unstable enough that picking wrong is expensive.
Four names keep coming up when developers evaluate this space right now: ElectricSQL, PowerSync, Zero from Rocicorp, and Triplit. Every single one of them has already pivoted, rebuilt, or lost its funded team once. That's not a knock — it's the most useful fact about this category, and it's the one most comparison posts skip in favor of feature checklists. This piece covers the checklists too, but the throughline is: you're not just picking an architecture, you're picking a bet on which vendor is still standing behind their sync protocol in eighteen months.
Why this comparison matters right now
Three trends converged to make sync engines a live decision instead of a research curiosity. Collaborative, Figma- and Notion-style UX is now a baseline expectation for SaaS products, not a differentiator — which means "real-time, multi-user, works offline" moved from nice-to-have to table stakes for a much larger set of apps than before. Second, a wave of VC-funded startups built genuinely different answers to the same problem between 2022 and 2025, so there's no longer just Firebase-or-roll-your-own; there are several credible, opinionated products competing for the same integration point in your stack. Third — and this is the part that makes 2026 specifically the moment to care — several of those products have already changed shape under their early adopters, which means the risk profile of this decision is now visible instead of theoretical.
There's also a quieter driver worth naming: AI-assisted coding has made rewriting a data layer cheap enough that developers are willing to try, discard, and re-try a sync engine mid-project in a way that would have been unthinkable when a migration meant weeks of manual plumbing. That changes the calculus — it means more teams are actually evaluating these tools empirically instead of picking one off a landing page and living with the consequences, which is exactly why the production evidence below is more useful now than it would have been two years ago.
The clearest illustration of the vendor-risk problem is a first-hand account from a developer building a real-time, Figma-like collaborative font editor, documented on their blog in March 2026. Their requirements were specific and common: real-time multiplayer editing, tens of thousands of records per project shared across tens of collaborators (not millions), fast local-first writes, and minimal custom sync plumbing. They tried Triplit, then ElectricSQL, then Livestore, then Zero — in that order, over roughly a year — before landing on something that worked, using an AI coding agent to accelerate each rewrite. That's not an outlier story about one indecisive engineer; it's a fairly representative tour of the category, and it's referenced throughout this piece because it's the closest thing to ground truth this space currently has: a builder who actually shipped on each of these, rather than a landing page describing what each one promises.
Their detour through Livestore is worth a beat even though it's not one of the four tools profiled here: Livestore runs largely on Cloudflare's D1 as the backing SQLite store, performed well, and is dogfooded in a real production app called Overtone. It turned out to be a poor fit for the font editor for one specific, architectural reason — Livestore currently models one user to one SQLite instance, which makes sharing data across users workable only with workarounds. That's a useful data point on its own: it's evidence that "sync engine" isn't one problem with four solutions, it's a family of related problems (per-user offline data, cross-user shared data, presence, conflict resolution) and each tool optimizes for a different subset of them. Livestore's per-user model is excellent for Spotify-like apps with lots of private data and little cross-user sharing; it's the wrong tool entirely for a Figma-like app, which is exactly the kind of mismatch a feature table won't surface but a production migration will.
What each tool actually does
ElectricSQL is, as of its current iteration, a read-path sync engine for Postgres. It streams filtered subsets of Postgres tables — called Shapes — to clients over plain HTTP. It deliberately does not sync writes: you build your own API for that, the same way you always have. The pitch is "keep your existing backend, add live-updating reads on top of it," which makes it the lowest-commitment option of the four if you already run Postgres and mostly need read-side reactivity (dashboards, activity feeds, live lists).
PowerSync is full bidirectional sync: server data flows down into a real, persistent SQLite database on the client (web, mobile, or desktop), and client writes flow back up through a local upload queue that a developer wires into their own API. It supports Postgres via logical replication, MongoDB via change streams, and MySQL via binlogs as source databases. The pitch is "your app works completely offline, indefinitely, and syncs cleanly when it reconnects" — a mobile-first promise, and one PowerSync has been iterating on since well before this current wave of competitors existed.
Zero, built by Rocicorp — the team behind the earlier Replicache — takes a query-driven approach. Instead of syncing whole tables or maintaining static sync-rule definitions, you write ordinary-looking queries in your application code, and Zero figures out what needs to be synced into a normalized local datastore to satisfy them. Reads and writes hit that local store first and reconcile with the server in the background, with the server treated as authoritative — it can accept or reject mutations. The pitch is "instant, reactive UI with minimal custom sync plumbing," aimed squarely at web apps built on a modern TypeScript stack.
Triplit bundles sync, a real-time query engine, and the database itself into one package — the "batteries included" option, requiring the least separate infrastructure to get a first prototype running. It ships its own TypeScript-native query and schema API, runs an embedded triple store under the hood, and was explicitly designed so a solo developer could add real-time, offline-capable data to an app without standing up a separate replication service. The catch, covered in detail below, is that the team building it no longer works on it as a funded product.
It's also worth being precise about what "sync engine" excludes here. None of these four tools are general real-time messaging systems (think Pusher or Ably) or CRDT text-editing libraries (think Yjs) — they're specifically about keeping a client-side copy of structured, queryable data consistent with a server-side database, which is a narrower and, for most CRUD-shaped apps, more directly useful problem than generic pub/sub.
How each is actually built
The architectural fork that matters most here isn't features, it's how much of the sync problem each tool is willing to own.
ElectricSQL runs as a standalone Elixir service that connects to Postgres via logical replication, reads the write-ahead log, and serves Shapes to clients over HTTP using long polling. Because it's plain HTTP, Shape data is cacheable by a CDN for fan-out to many clients — a genuinely nice property for read-heavy, high-fan-out apps. There's no mandatory client-side database; data can live as an in-memory materialized map, or you can pair Electric with PGlite, the same team's embeddable Postgres build for the browser, if you want a fuller local Postgres. What Electric conspicuously does not do is decide what happens to a write — that's entirely your API's problem, though the team's own TanStack DB integration tries to soften the DIY write path.
PowerSync runs a separate sync service (self-hosted or via PowerSync Cloud) that also connects via logical replication, but stores its own operational bucket data in a pluggable persistent store (currently MongoDB). On the client, PowerSync maintains a genuine local SQLite database, and writes go into a durable upload queue that your app processes with a developer-defined uploadData() function — so conflict resolution is still your responsibility, but the plumbing for offline durability is handled for you. PowerSync originally organized synced data into "buckets" defined by Sync Rules (parameter queries plus data queries); it has since layered "Sync Streams" on top as a more reusable, parameterized way to define the same thing.
Zero's server-side component replicates from your database and serves a normalized client datastore backed by IndexedDB in the browser. What's different is the authorization model: because what syncs is expressed as a query rather than a static rule or a whole-table shape, per-row access control can be expressed as constraints on those same queries, instead of a separate permissions DSL layered on top. In production use, this reportedly integrates cleanly with Drizzle ORM and keeps the client bundle small — but it ships without built-in multiplayer presence (live cursors, "who's online"), which has to be built as separate infrastructure if your app needs it.
Triplit collapses the sync layer and the database into one embedded, batteries-included system, trading architectural purity for the fastest path from zero to a working real-time prototype.
Client platform coverage is another quiet differentiator worth checking before you commit. PowerSync's SDKs reflect its mobile-first origins, with native support spanning web, iOS/Android, Flutter, React Native, and Kotlin Multiplatform — a direct consequence of the offline-for-hours-or-days use case it was built for. Electric and Zero are, today, primarily JavaScript/TypeScript-and-web-first projects; you can reach mobile through the same web runtime patterns (React Native, Capacitor-style wrappers), but neither has the breadth of native mobile SDKs PowerSync does. If your roadmap includes a native mobile app in the next year, that gap is worth weighing more heavily than any of the sync-protocol differences above it.
What changed — and why it's the real story
This is the part every landing page leaves out, and it's arguably more decision-relevant than any architecture diagram.
ElectricSQL rebuilt itself from the ground up in July 2024. The original ElectricSQL was a CRDT-based, full offline-write system with automatic conflict resolution — a much larger, more ambitious scope. The team found it too complex to make stable and reliable, stopped development on it entirely, and shipped a deliberately smaller "electric-next" (now just "Electric Sync") that dropped CRDTs and, with them, automatic write-conflict resolution. If you adopted Electric before mid-2024 expecting offline writes to just work, that promise no longer exists in the current product.
Rocicorp's Zero is literally attempt number three at this problem from the same team, following Replicache's mutator-and-rebase model (conceptually similar to git rebase: local mutations apply optimistically, then get replayed on top of whatever the server says is canonical). Replicache is being superseded by Zero, which is a reasonable evolution — but it means anyone who built on Replicache is on a product whose own creators have moved on to a different architecture.
Triplit's shift is the sharpest one. In October 2025, Supabase announced that Triplit co-founder Matt Linkous was joining Supabase — explicitly described as bringing his offline-first expertise to help Supabase build third-party integrations with, notably, Electric, Zero, and PowerSync (i.e., Triplit's own competitors), not to fold Triplit into the Supabase product. Supabase's own framing is worth reading carefully: the stated plan is to further open-source the Triplit codebase and document what they learned, but there's no funded team shipping Triplit going forward. It's now community-maintained. That's the acquihire pattern familiar from other categories, applied here for the first time to a sync engine developers were building production apps on.
PowerSync's change is smaller in comparison — Sync Rules evolving into the newer Sync Streams abstraction — but it's a real API surface change for anyone who adopted the earlier model, and a reminder that even the most "mature" option in this group is still actively reworking its core abstractions.
Put the four side by side and a pattern emerges that no single vendor's changelog will state outright: nobody in this category has shipped a stable, unchanged core abstraction for more than about two years. That's not necessarily a red flag — it's a young category still finding its shape, and rapid iteration is how PowerSync earned its "most mature" reputation in the first place. But it does mean "which architecture is best" is the wrong first question. The better first question is "how much of my application logic is expressed in this tool's abstractions, and how painful is it if those abstractions change again" — which is precisely the question the font-editor migration account above answers empirically, four times over, in a single project.
Why developers should actually care
Cost. Electric and PowerSync both offer a genuine open-source, self-hostable path plus a metered managed cloud service, so cost scales with usage and you retain an exit option. Zero's hosting story is younger and less turnkey — most teams currently self-host the zero-cache replication service themselves. Triplit's cost calculus changed overnight in October 2025: there's no vendor cloud tier backed by a funded company to lean on, so the real cost is now internal engineering time to maintain and patch it yourself.
Latency and DX. This is where the production account matters most: the same developer who found Electric's long-polling transport "slow and brittle" in practice, and its DIY write path "an uphill battle" even with TanStack DB's help, found Zero's local-first reads/writes "basically flawless" after a migration, with a notably small client footprint. That's one data point, not a benchmark suite — but it's a real production comparison, which is more than most vendor pages offer.
Lock-in. All four of these tools embed themselves deep in your data layer: your ORM choice, your permission model, and often your write-path shape all end up coupled to the sync engine's opinions. Migrating later is not a config change — the account referenced throughout this piece did it four times in about a year, using an AI coding agent to accelerate the rewrite each time, and it still cost real calendar time.
Security. Electric's Shapes are, functionally, an HTTP endpoint serving filtered rows — which means access control has to be deliberately designed into how you define and gate each Shape (the project ships a dedicated Auth guide for exactly this reason); getting it wrong risks over-broad data exposure, especially since Shape responses are CDN-cacheable by design. PowerSync and Zero push more of the authorization decision through logic you control on the write path and, for Zero, through the query definitions themselves.
Maintainability. The single biggest maintainability risk in this category right now isn't a bug — it's vendor continuity. Triplit is the cautionary tale, but Electric's own 2024 rebuild shows that even actively-funded teams will drop major architectural promises (CRDT-based offline writes) if they can't make them reliable at scale. Concretely, that risk shows up as work: when the font-editor developer walked away from Electric after roughly two months of trying to make the DIY write path and long-polling transport perform acceptably, and later migrated a working Zero integration into place "shortly" with an AI coding agent doing much of the mechanical translation, the lesson wasn't "AI makes migrations free" — it was that the choice of engine still determined whether that two months was spent on your product or on fighting your infrastructure. A maintainability-conscious pick is one where, if the vendor disappears tomorrow, the abstraction you're left holding is simple enough to maintain yourself; that argument favors Electric's narrower scope and PowerSync's longer track record over Zero's younger, more ambitious surface area and Triplit's now-orphaned one.
Practical use cases
- ElectricSQL fits teams with an existing Postgres-backed app who want incremental, low-commitment live reads — dashboards, activity feeds, collaborative-but-mostly-read views — without touching their existing write API. The project's own demos (an agentic system called "Burn," and a project-management app called "Linearlite") both lean into this read-heavy pattern paired with PGlite.
- PowerSync fits mobile and field-work apps that must function with zero connectivity for extended periods — logistics, healthcare, industrial — where a team can accept running a dedicated sync service in exchange for the most battle-tested offline story of the four.
- Zero fits TypeScript-first web teams building new collaborative SaaS from scratch, especially those already using Drizzle, who want instant local reads and writes without hand-building a caching layer, and who are willing to build presence/multiplayer cursor infrastructure separately.
- Triplit fits prototypes, hackathons, and small internal tools where getting to a real-time demo fast matters more than a five-year support horizon — with the explicit expectation that you may need to migrate off it later.
The limitations marketing tends to omit
Electric's "simple, Postgres-native" pitch is real, but "simple" is doing a lot of work — it's simple because it refuses to own your write path or your conflict resolution at all, which is a very different promise from "handles sync for you." PowerSync's "most mature" positioning is earned, but that maturity comes bundled with the most infrastructure to operate: a separate sync service, a pluggable storage backend to run, and a rules/streams DSL to keep in sync with your schema. Zero's "instant, reactive" story is credible in early production use, but it's the youngest of the four in the field, has no built-in presence layer, and its self-hosting story is less proven than PowerSync's. Triplit's "full-stack, batteries-included" copy predates October 2025 and, as of this writing, doesn't foreground that the founding team has moved on to work on integrations at a different company.
Comparison table
| Dimension | ElectricSQL | PowerSync | Zero | Triplit |
|---|---|---|---|---|
| Sync direction | Read-only (server → client) | Bidirectional | Bidirectional | Bidirectional |
| Client storage | In-memory map, or PGlite for full local Postgres | Real local SQLite | Normalized store over IndexedDB | Embedded database |
| Write path | Your own API — Electric doesn't touch writes | Local upload queue → your uploadData() → your API |
Server-authoritative mutators; server can accept/reject | Built into the database itself |
| Conflict resolution | N/A (no write sync) | Developer-implemented | Server-authoritative reconciliation | Built-in |
| Source databases | Postgres (logical replication) | Postgres, MongoDB, MySQL | Postgres-based replication | Self-contained |
| Transport | HTTP long polling, CDN-cacheable | Persistent sync service connection | Continuous background sync | Internal protocol |
| Backend to run | Elixir Electric service | PowerSync sync service + storage backend |
zero-cache replication service |
None separate — it's embedded |
| Hosting options | Self-host (OSS) or Electric Cloud | Self-host (OSS) or PowerSync Cloud | Mostly self-hosted today | Self-hosted / community only |
| Team/backing (2026) | Actively funded, rebuilt core once (2024) | Actively funded, longest track record | Actively funded, Rocicorp's third attempt | Founders acquihired by Supabase (Oct 2025); community-maintained |
| Best fit | Postgres shops adding live reads incrementally | Offline-critical mobile/field apps | New TypeScript web apps wanting instant local UX | Fast prototypes, low long-term commitment |
An independent read
Strip away the marketing and the single most predictive variable in this comparison isn't sync protocol elegance — it's how much of the hard problem (writes, conflicts, offline durability) each tool is actually willing to own, and how stable the team behind that ownership has proven to be. Electric's honesty about not owning writes is refreshing but means you're still building a real system yourself. PowerSync owns the most and has the track record to back the claim, at the cost of running more infrastructure. Zero is the most ambitious technically — collapsing sync into ordinary queries is a genuinely elegant idea — but it's asking you to bet on a young product from a team that has now built three different sync engines, which cuts both ways: they've learned a lot, and they've also walked away from two previous approaches. Triplit is no longer a fair fight; treat anything you build on it today as disposable.
Who should pick what
If you already run Postgres, mostly need live-updating reads, and can live with hand-rolling (or TanStack-DB-assisting) your write path — ElectricSQL. If you're shipping to field workers or mobile users who need the app to keep working with no connectivity for hours or days, and your team can operate an extra service — PowerSync. If you're a TypeScript-first web shop starting fresh, want the least custom sync code, and are comfortable building presence features yourself on a newer stack — Zero. If you're prototyping, demoing, or building something you expect to rewrite within a year regardless — Triplit is genuinely fine, just don't put it on your production critical path without budgeting for that rewrite.
None of these are wrong choices in the abstract. They're different bets on who does the hard work — you, the vendor, or nobody — and, as of 2026, on which of these vendors is still around to help when it breaks.
Discussion: If you've shipped a real app on one of these — or migrated between them like the developer referenced above — what actually broke in production that the docs didn't warn you about: the conflict resolution, the auth model, the ops burden of running the sync service, or something else entirely?
Sources:
- Triplit joins Supabase
- Choosing a Sync Engine for Local-First in 2026 — johnny.sh
- ElectricSQL electric-next Vs PowerSync — PowerSync Blog
- ElectricSQL vs PowerSync vs Replicache — QueryPlane Blog
- Sync Engines Compared: ElectricSQL vs Convex vs Zero (2025) — merginit
- Zero Documentation — Introduction
- Electric Sync Documentation
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