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Developer Tools · head to head

PartyKit vs Unit21

P

PartyKit

Developer Tools

Platform for building and deploying realtime multiplayer servers on the edge

From
Free
Free plan
Yes
Full reviewWebsite
Unit21 logo

Unit21

Cybersecurity

No-code fraud and AML risk operations platform for fintechs and neobanks

From
On request
Free plan
No
Full reviewWebsite

The short version

  • Only PartyKit has a free tier, so it costs nothing to try first.
  • Each has a real cost: PartyKit documentation and FAQ material on the marketing site is sparse compared to larger realtime platforms.; Unit21 it is built for fintech scale rather than card issuer scale, so organisations reaching very high transaction volumes generally re-evaluate against heavier platforms and face a migration.
  • They diverge on capability: PartyKit covers Stateful edge servers, Unit21 covers No-code rule builder.
  • Prices and features above were last checked on 1 September 2026.

Where they differ

Only the attributes on which PartyKit and Unit21 actually diverge.

Attributes where PartyKit and Unit21 differ
AttributePartyKitUnit21
Starting priceFreeOn request
Pricing modelfreemiumquote
Free tierYesNo
Platformsweb, apiWeb
CategoryDeveloper ToolsCybersecurity

Identical on both: user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in PartyKit

  • Stateful edge servers
  • WebSocket-first API
  • CRDT library compatibility
  • Framework integrations
  • Global edge deployment
  • Custom domains

Only in Unit21

  • No-code rule builder
  • Case management
  • SAR filing
  • Backtesting
  • Identity and device signals
  • Data ingestion API

What people use each for

The jobs each tool is most often brought in to do.

PartyKit

  • Multiplayer collaborative appsnot Unit21
  • Realtime AI agent backendsnot Unit21
  • Live cursors and presencenot Unit21
  • Collaborative whiteboards and documentsnot Unit21

Unit21

  • A neobank whose sponsor bank requires a documented monitoring programme before it will keep the BIN sponsorshipnot PartyKit
  • A crypto exchange needing SAR filing and case management without building an internal compliance engineering teamnot PartyKit
  • A payments startup where the fraud lead needs to ship a new rule the same day a new attack pattern appearsnot PartyKit
  • A lender consolidating fraud alerts from three point tools into one investigator queue with a single audit trailnot PartyKit

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

PartyKit

  • Documentation and FAQ material on the marketing site is sparse compared to larger realtime platforms.
  • Commercial free tier requires deploying to the user's own Cloudflare account, adding setup complexity.
  • Storage on the free Individual plan clears every 24 hours, limiting it to prototyping rather than persistent production data.
  • Smaller ecosystem and community than more established realtime infrastructure providers.

Unit21

  • It is built for fintech scale rather than card issuer scale, so organisations reaching very high transaction volumes generally re-evaluate against heavier platforms and face a migration.
  • No-code rule authoring shifts power to the risk team, which is the point, but without governance it produces rule sprawl that nobody can explain to an examiner two years later.
  • Detection quality depends on the signals you feed it, so a thin integration produces thin results and the platform cannot compensate with proprietary consortium data the way larger vendors do.
  • Pricing is quoted by volume with an annual commitment, so a fintech whose growth stalls pays for headroom it did not use.
  • SAR filing coverage is oriented to United States FinCEN reporting, so firms filing in the United Kingdom, European Union or Asia handle those submissions outside the tool.

Pricing, plan by plan

PartyKit

Free
  • IndividualFree
    • Up to 10 live projects
    • Deploy to the global edge platform
    • Storage clears every 24 hours
  • CommercialFree
    • Unlimited projects
    • Custom domains
    • Runs on your own Cloudflare account; pay only Cloudflare usage

Unit21

On request
  • Unit21 Platform$undefined/year
    • Priced by monitored volume and modules, annual contract
    • Fraud, AML and case management packaged separately
    • Implementation and historical data backfill quoted with the subscription

Which should you pick?

Choose PartyKit if

  • You need stateful edge servers.
  • You want to start without paying.
  • You work on web, api.
  • You also want websocket-first api.
PartyKit review

Choose Unit21 if

  • You need no-code rule builder.
  • You also want case management.
Unit21 review

Questions people ask

Is PartyKit or Unit21 better?
Neither clearly leads. PartyKit starts at Free and Unit21 at On request, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, PartyKit or Unit21?
PartyKit has a free tier; the other does not. Paid plans start at Free for PartyKit and On request for Unit21.
Does PartyKit or Unit21 run on more platforms?
PartyKit runs on web, api. Unit21 runs on Web.
Can I use PartyKit for free?
Yes. PartyKit has a free tier, so you can try it without paying. Unit21 starts at On request.
What is PartyKit best used for?
PartyKit is most often used for multiplayer collaborative apps, realtime ai agent backends, live cursors and presence, collaborative whiteboards and documents. Of those, multiplayer collaborative apps and realtime ai agent backends are not what Unit21 is typically brought in for.
What can PartyKit do that Unit21 cannot?
PartyKit covers Stateful edge servers, WebSocket-first API, CRDT library compatibility, Framework integrations. Unit21 covers No-code rule builder, Case management, SAR filing, Backtesting.

Answered from the vendors’ own pages

PartyKit: How much does PartyKit cost?

PartyKit is completely free. Both the Individual and Commercial plans have no upfront costs.

Source
Unit21: Do we need engineers to run it?

Only for the initial data integration. After that the design intent is that risk and compliance staff author and deploy rules themselves.

PartyKit: What is PartyKit's Individual plan?

The Individual plan is free and includes deployment to a global edge platform, support for up to 10 live projects, and is suitable for small projects. Storage is cleared every 24 hours.

Source
Unit21: Does it file SARs?

Yes, it generates and electronically files suspicious activity reports to FinCEN. Non-US regimes are not covered to the same depth.

PartyKit: What is PartyKit's Commercial plan?

The Commercial plan is free but requires deploying to your own Cloudflare account. It includes custom domains, unlimited projects, and you pay only your Cloudflare usage costs.

Source
Unit21: Can we test a rule before it goes live?

Yes. Backtesting against historical data to see projected alert volume is one of the more useful parts of the product, because alert volume is the real cost.

PartyKit: Can I upgrade from Individual to Commercial plan?

Yes, both plans are free but offer different feature sets. The Commercial plan removes project restrictions but requires managing your own Cloudflare infrastructure.

Source
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