Prismm Is Shutting Down — The Best Alternative for Wedding Couples | Untangly

If you used Prismm for your wedding seating chart, you've probably already heard the news: Prismm is shutting down. Cvent acquired Prismm (formerly AllSeated) in April 2025, and the standalone platform is going offline December 31, 2026.

But "December 31" makes it sound like you have time. You don't — not if you're planning a wedding right now.

Here's what's actually happening, and what to do instead.

What's Happening With Prismm, Exactly

Cvent bought Prismm and is migrating customers to Cvent Event Diagramming (formerly Social Tables). The transition timeline:

July 8 – September 30, 2026: New event creation ends, rolling out account by account
October 1, 2026: Prismm becomes view-and-export only — no new edits
December 31, 2026: Platform goes offline entirely
Events before January 1, 2022: Won't be migrated to Cvent at all

So if you're trying to plan a 2026 or 2027 wedding on Prismm right now, you may already be locked out of creating a new event.

Why Cvent Isn't the Right Answer for Wedding Couples

Cvent is offering their Event Diagramming tool as the migration path. It's a professional venue management platform — and that's exactly the problem.

Cvent Event Diagramming is built for venues and corporate event planners managing hundreds of events. It costs hundreds to thousands of dollars per year. Your templates, favorites, and saved objects from Prismm don't transfer over. Events older than January 2022 won't even be accessible.

And most importantly: it doesn't solve the problem that wedding couples actually have. Cvent can diagram a room. It cannot tell you that your uncle and your dad's business partner haven't spoken in eight years and should never be at the same table.

What Wedding Couples Actually Need

Prismm was (genuinely) excellent at one thing: making your venue look beautiful in 3D. If you're a wedding planner or venue manager who needs professional-grade floor plan visualization for client presentations, Prismm's migration to Cvent Event Diagramming actually makes some sense.

But most couples used Prismm for one purpose: figuring out who sits where.

And for that problem, you need a tool built around guests and relationships, not room dimensions. You need something that:

Lets you track RSVPs and seat guests in the same place
Handles "keep together" and "keep apart" rules
Updates automatically when RSVPs change last-minute
Actually tells you when your seating plan has a conflict

Prismm never did any of that. The migration to Cvent doesn't add it. That's the gap.

The Best Prismm Alternative for Wedding Couples: Untangly

Untangly is an AI-powered wedding seating chart tool designed from the ground up for exactly the situations Prismm couldn't handle.

What's different:

| | Prismm / Cvent | Untangly | |---|---|---| | Built for | Venues & event managers | Wedding couples & planners | | Price | $$$–$$$$ enterprise | Free up to 50 guests, $19/event for unlimited | | Relationship rules (keep apart/together) | No | Yes | | AI optimization | No | Yes — runs thousands of combinations | | Harmony score (conflict detection) | No | Yes | | Last-minute RSVP updates | Manual | Re-run AI in seconds | | Templates transfer | No (lost in migration) | Start fresh in minutes | | 3D venue floor plans | Yes | No (we focus on guest logic, not room design) |

If you need a professional 3D floor plan for your venue, you'll want to look at Cvent or SeatedWithLove for the venue side. But if you need a seating chart that actually solves the hard part — the people — Untangly is built for you.

Other Prismm Alternatives Worth Knowing

SeatCanvas

A lightweight, browser-based seating chart tool. Free up to 40 guests, $9.99 one-time for larger events. Good for simple guest lists with no relationship complexity. No AI optimization.

SeatPlan.io

Free drag-and-drop seating planner, unlimited guests, no signup required to start. You pay to save, share, or export. Great for couples who want to sketch out a basic plan quickly. No conflict detection.

SeatLogic

Purpose-built AI seating optimizer — probably the closest competitor to Untangly. Free up to 250 guests, paid tier for the AI optimizer. Worth comparing if you want to evaluate AI tools head-to-head.

The Knot / WeddingWire

If you're already using one of the big wedding platforms, their built-in seating tools are free. Basic drag-and-drop, no AI, but convenient if your guest list is simple and drama-free.

PerfectTablePlan

Desktop software ($29.95–$39.95 one-time) that's been around for 20+ years. Good for couples who prefer working offline. No AI optimization, no real-time collaboration, no mobile access.

How to Migrate Away From Prismm in 10 Minutes

If you have existing data in Prismm, here's how to bring it over before it goes read-only:

Export your guest list from Prismm as a CSV (Guest List → Export)
Export your current seating plan as a PDF (for your own records)
Sign up for Untangly — free for up to 50 guests, no credit card needed
Import your guest CSV — Untangly maps columns automatically (name, email, RSVP status, table)
Set up your tables — recreate your table count and sizes (takes ~3 minutes)
Add relationship rules — this is where Untangly actually adds value Prismm never had
Run the AI optimizer — get your first conflict-free arrangement in under 60 seconds

You won't miss the 3D room visualization for the seating problem. And you'll gain the thing Prismm never gave you: a seating chart that accounts for the people, not just the furniture.

Start free — no credit card needed →

Frequently Asked Questions

Is Prismm actually shutting down?

Yes. Prismm (formerly AllSeated) was acquired by Cvent in April 2025. The standalone platform is sunsetting December 31, 2026. New event creation stopped rolling out July 8, 2026. The platform goes view-only on October 1, 2026.

What happens to my Prismm data when it shuts down?

Events dated January 1, 2022 or later can be viewed in Cvent Event Diagramming after the migration. Events older than January 1, 2022 will not be accessible — you must export them before the shutdown. Templates, favorites, and object groups are not transferred.

Is Cvent Event Diagramming a good Prismm alternative for wedding couples?

For venue managers and professional event planners: possibly. For wedding couples planning a single event: no. It's a complex enterprise tool designed for venue management teams, not couples building a 150-person wedding seating chart. The pricing and learning curve are both significant.

What's the best free Prismm alternative?

For wedding couples: Untangly (free up to 50 guests), SeatPlan.io (free to design, pay to export), or SeatCanvas (free up to 40 guests). If you need AI-powered optimization and relationship management for a larger wedding, Untangly's Garden plan is $19 per event.

Does Untangly have 3D floor plan visualization like Prismm?

No. Untangly is focused on the guest-relationship side of seating — who sits where based on social dynamics, not how the room looks in 3D. If you need 3D venue visualization for planner presentations, look at Cvent Event Diagramming or SeatedWithLove. Most couples find they don't need 3D visualization for the seating problem itself.