---
title: "Compare Gessa to Unity and Unreal"
description: "How to read the Gessa comparison pages, the four moats they lead with, and the honesty contract every parity cell is held to."
engineVersion: v1.0.234
date: 2026-09-28
license: "(c) Gessa, proprietary. Cite with attribution to https://gessa.ai/docs/. Terms: https://gessa.ai/terms/."
canonical: https://gessa.ai/docs/compare/index/
---

# Compare Gessa to Unity and Unreal

_Last verified 2026-09-06 against engine v1.0.232. Competitor sources were accessed 2026-09-06; every Gessa cell binds to the generated engine reference and the build fails if a bound surface disappears._

These pages compare Gessa to Unity and to Unreal Engine on the axes where the difference is real and defensible, and they name Gessa's gaps on the same page as its strengths. They are not marketing copy: every row is held to a machine-checked honesty contract.

## The honesty contract

Each comparison row has a Gessa side and a competitor side, and each side is a validated Markdoc cell.

- The Gessa cell, {% gessaCell status="supported" binds="RigidBodyComponent" /%} in source, carries a closed status value (supported, partial, not yet, or unknown) and a `binds` that names the live engine surface it stands on: a capability in the generated capability catalog, a component contract, an engine-capability-graph key, or a `check:` gate in the build. A cell that claims support or partial support must bind to a surface that still resolves, so a comparison claim cannot outlive the capability it names. This is enforced by `check:docs-claims`.
- The competitor cell renders as a dated source chip that links to the competitor's own documentation and carries the engine version and the date the page was last read. `check:docs-claims` fails the build on a missing attribute or an unparseable access date, so a competitor claim is never unsourced.

Competitor documentation moves, so the version and access date are load-bearing. When a competitor cell reads Unreal 5.8 or Unity 6000.3, that is the documentation edition the claim was checked against, not a guarantee about a newer release.

## The comparison pages

Each page leads with a defensible moat and names Gessa's concession on the same page:

1. [Browser-native 3D engine, no install](browser-native-engine.md). Gessa renders and publishes in the browser. The concession: no Nanite-class virtualized geometry, and dynamic global illumination is baked rather than Lumen-class.
2. [Server-authoritative multiplayer without a netcode plugin](server-authoritative-multiplayer.md). Authority, prediction, lag compensation, replication, and replay ship in the engine. The concession: no rollback (by design), single region in this release, first-generation interest management.
3. [Agent-native authoring over MCP](agent-native-authoring.md). Human and agent authoring run through the same capability surface with a parity floor. The concession: physics-family depth is thinner than either competitor.
4. [Deterministic, replay-verified physics](deterministic-physics.md). A fixed-timestep Rapier core with a golden-corpus determinism gate and a recast navmesh. The concession: scalar-mass v1, and no cloth, soft body, destruction, vehicle, or ragdoll families.
5. [Instant multiplayer worlds vs open-world streaming](instant-worlds-vs-open-world-streaming.md). Gessa publishes interest-managed worlds that play instantly. The concession: it is not an open-world engine, with no automatic large-world streaming, engine-native procedural generation, or weather.

Gessa is not an open-world streaming engine. The [netcode model](../explanation/netcode-model.md) describes the authority and interest-management boundaries of its multiplayer worlds.

## What Gessa does not claim

The proof gates behind these pages certify one thing: that every parity cell stands on something real at the pinned engine version. `check:docs-claims` fails the build unless each Gessa cell that reads supported or partial binds to a live capability id, component contract, capability-graph key, or `check:` gate, and unless each competitor cell carries an engine, version, URL, and a real access date. The determinism, replay, and navmesh claims these pages lean on are the ones `check:physics-golden-corpus`, `check:runtime-replay-release-gate`, and `check:navigation-canon` assert in the build. Those gates certify that a cell is bound and dated, not that the engine as a whole is finished or that any world is end-to-end playable. Where a competitor is genuinely ahead, the page says so in a conceded-strengths section and links to the competitor's own documentation for it. Capabilities Gessa does not offer at all are named in the trust center, not omitted here.