Unreal Engine replication failures are often silent.

A replicated variable changes on the server but never reaches a client. A Server RPC called from a Widget appears to do nothing. A Multicast is fired on an actor that is not replicating. An actor is missing on one client because of ownership, relevancy, dormancy, cull distance or net-driver state.

And in many of these cases, Unreal gives you no compile error and little more than a line in the Output Log — if anything at all.

The usual workflow is familiar: add Print Strings, open multiple PIE windows, compare logs, guess, test again.

Replication Doctor replaces trial and error with direct evidence.

Documentation: Download

THE SOLUTION

Replication Doctor is an editor-only diagnostics suite for Unreal Engine networking. It helps you find replication problems both before Play and while a multiplayer session is running.

Before Play, the Static Replication Audit scans Blueprints and native classes for configuration mistakes that break networking. It detects issues such as replicated variables on actors with Replicates disabled, RPCs declared on classes with no network callspace, missing RepNotify functions, Server RPCs placed in Level Blueprints, Multicasts on non-replicating actors, replication-disabled components and more.

Every finding identifies the responsible property, function or node, explains why it matters, and classifies the issue by severity and fix type.

Where a correction is safe and deterministic, Replication Doctor can preview and apply it for you with source-control checkout, transactional changes, batch recompilation and a persistent Revert manifest.

During Play, the Live Session view shows the server and every connected client side by side in a single Actor Matrix.

If an actor is missing on a client, Replication Doctor does not simply say “not replicated.” It attempts to identify the exact gate responsible: not registered with the net driver, dormant for that connection, outside cull distance, owner-only but not owned by that client, or another supported replication state.

Select an actor and the Ownership Explorer visualizes its owner chain to the connection, marks where the chain breaks, and helps expose one of the most common causes of failed Server RPCs.

The RPC Prediction table then evaluates each RPC per client as Absorbed, Remote, Local or Unavailable. When a Server RPC would be absorbed, the tool distinguishes between separate causes such as an actor with no remote role and an actor for which the net driver cannot resolve an owning connection.

Enable the RPC Monitor to capture real calls while you play. Sends and executions are correlated into Sent, Delivered, Local, Queued and Dropped states, with a reason attached to each captured call.

WHY IT SAVES TIME

Replication bugs are rarely difficult because the final fix is complicated. They are difficult because the engine often gives you too little information about why something did not happen.

A single missing Replicates flag, invalid RPC location or broken ownership chain can cost hours of Print String debugging.

Replication Doctor is designed to shorten that investigation.

Instead of asking:

“Why is this actor missing on Client 2?”

you can inspect one matrix cell and see the replication gate and supporting values.

Instead of asking:

“Why does this Server RPC do nothing?”

you can inspect the ownership chain, prediction result and captured RPC state from one place.

No custom gameplay framework. No runtime dependency. No components to add. No base classes to inherit from. No custom Blueprint architecture required.

All four plugin modules are Editor modules, so Replication Doctor adds no runtime footprint to your packaged game.

WORKFLOW

Open Tools > Replication Doctor.

On the Audit page, run Quick Scan for fast registry/reflection-based analysis. It avoids loading every Blueprint and is designed to return useful results within seconds even in larger projects.

Findings are grouped by rule and include:

• Severity
• Evidence
• A clear explanation
• Fix classification
• Jump-to-node navigation
• Optional suppression with a required reason

Preview Safe fixes before applying them. Replication Doctor batches changes, recompiles affected Blueprints and records a dedicated Revert manifest because Blueprint recompilation can replace the class default object and make normal editor Undo unreliable for this workflow.

Run Full Scan when you want every Blueprint in scope checked. Full Scan is chunked, cancellable and incrementally cached to keep the editor responsive and make repeated scans faster. It is intentionally blocked during PIE, while Quick Scan remains available.

Switch to Live Session and start a supported PIE multiplayer session.

Replication Doctor validates your Play settings first and can safely correct supported settings without changing your chosen network mode.

Once clients connect, the Actor Matrix fills. Select an actor to inspect ownership and RPC prediction, then enable recording in the RPC Monitor to capture what actually happens during play.

Export results as:

• Self-contained HTML
• CSV
• Schema-versioned JSON
• Clipboard-ready support package containing environment data and findings, without asset content

The included Broken Lobby demo map contains twelve deliberate replication bugs and three correctly configured actors. It exercises eight static rules plus common live-session states, giving you a practical introduction before scanning your own project.

KEY FEATURES

STATIC REPLICATION AUDIT

• Whole project, folder, selected assets or open Blueprint scope
• Quick Scan using Asset Registry and reflection only
• Full Scan with chunking, cancellation and incremental caching
• 13 rules covering common replication failures and risky configurations
• Detects non-replicating actors with replicated variables or RPCs
• Detects components with replication disabled
• Detects RPCs declared on classes with no valid network callspace
• Detects self-targeted invalid RPC call sites
• Detects missing RepNotify functions
• Detects Server RPCs in Level Blueprints
• Detects Multicasts on non-replicating actors
• Detects native Server RPCs without validation
• Detects GetGameMode usage in client-executing graphs
• Detects suspicious Net Update Frequency and cull-distance configurations
• Includes three opt-in experimental authority-path rules
• Evidence, severity and fix class for every finding
• Jump directly to the responsible Blueprint node
• Per-finding suppression with a mandatory committed reason
• HTML, CSV, JSON and support-package export

SAFE FIX SYSTEM

• One-click Safe fixes where the correction is deterministic
• Dry-run preview before modification
• Transactional changes
• Batch Blueprint recompilation
• Persistent Revert manifest that survives editor restart
• Source-control checkout attempted before modification
• Fixes blocked during PIE
• Fixes blocked for content outside the project folder
• Conservative handling of engine-specific exceptions such as AInfo-derived Blueprints

LIVE SESSION DIAGNOSTICS

• Automatic discovery of supported Listen Server and single-process Play-As-Client sessions
• Continuous Play-settings validation
• Actor Matrix comparing server and connected client worlds
• Sixteen-state replication gate ladder
• Named evidence for every supported actor/client state
• Dedicated Client-only group for client-spawned actors
• Automatic poll-rate throttling under a configurable time budget
• Ownership Explorer with visual owner-chain break detection
• RPC Prediction per client and per RPC
• Absorbed, Remote, Local and Unavailable prediction states
• RPC Monitor with Sent, Delivered, Local, Queued and Dropped states
• Persistent, exportable RPC timeline
• Safe delegate chaining so PIE Net Emulation continues to work alongside the monitor
• Lifecycle protection for PIE start/stop, Blueprint recompiles, disconnects and editor shutdown

EDITOR INTEGRATION

• Tools menu entry
• Level Editor toolbar button
• Content Browser folder context menu
• Content Browser asset context menu
• Blueprint Editor toolbar button
• Blueprint Editor Tools menu entry
• Project Settings and Editor Preferences pages
• Integrated under the Matify Games Doctor tool family

DESIGNED TO BE TRANSPARENT ABOUT LIMITATIONS

Unsupported or limited topologies such as Iris, multi-process PIE or standalone PIE are detected and explained instead of producing misleading results.

Heuristic findings are never promoted to Error severity.

Known limitations — including Legacy Replication support, editor-only operation, Windows 64-bit support, single-process PIE requirements, Quick Scan loading behavior and RPC Monitor visibility limits — are documented in the included manual.

Replication Doctor is built for one purpose:

Stop guessing why Unreal replication failed — and show the evidence instead.