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UEFN v39.00 Update : In-Island Transactions Publishing Date, Mobile Preview & Physics Tools

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UEFN v39.00 Update : In-Island Transactions Publishing Date, Mobile Preview & Physics Tools

Fortnite v39.00 Ecosystem Update: What UEFN Creators Need to Know

Fortnite v39.00 is a pivotal ecosystem update for Unreal Editor for Fortnite (UEFN) creators—especially anyone preparing to monetize with in-island transactions, optimize for mobile-first performance, or build deeper gameplay systems using physics, AI, and Scene Graph.

This release doesn’t just add tools—it clarifies timelines and raises the bar for compliance and operations. Epic confirms a firm publishing date for in-island transactions (January 9, 2026), continues consolidating analytics inside Creator Portal, expands mobile iteration tooling with Mobile Preview, and introduces major upgrades to physics debugging and Verse control.

Below is a structured breakdown of the biggest v39.00 changes, what they mean for creators, and what to do next. For full technical implementation details, rules, and reference material, readers should review Epic’s official v39.00 documentation.

Reminder: Legacy Analytics Site Retires December 10, 2025

Epic reiterates that the Legacy Analytics site is retiring on December 10, 2025, following the launch of the account-wide Monetization page in Creator Portal.

What Creators Should Expect

Action: If your team still relies on the legacy site for reporting workflows, migrate now—before Dec 10.

In-Island Transactions: Publishing Opens January 9, 2026

The most important line in v39.00 is the publishing update:

Publishing for in-island transactions will open January 9, 2026.

Epic is shifting the date to allow more time for testing and bug fixing before going live to players. You may see the Experimental flag removed, but publishing will not be live until Jan 9.

What’s New for Testing in v39.00

Epic expands what creators can test on their islands now (without deducting V-Bucks), including:

This is a major shift from “preview tooling” to “systems validation.”

Consequential to Gameplay: New Requirement

Epic adds a critical classification rule: items that provide meaningful gameplay advantages are considered Consequential to Gameplay.

This is both a design constraint and a compliance requirement—particularly important for competitive modes, progression systems, and paid access gating.

Developer Rules Updates: New Disclosure Requirements

Epic urges creators to re-check the Fortnite Developer Rules, citing new rules specifically for disclosures:

If you’re building paid progression, paid zones, or purchasable power, this is mandatory reading.

Update to Publishing Terms: Fortnite Developer Agreement

Epic notes a major terms change:

Action: Treat this like a production blocker—ensure the account owner/admins accept the updated agreement before your next publish window.

Mobile Updates: Mobile Preview + Improved Touch Controls

v39.00 adds multiple features aimed at supporting mobile-first development, which matters more than ever as creator islands compete for broad device coverage.

Mobile Preview in UEFN

Mobile Preview allows you to launch a Fortnite session in a mobile mode with:

Known issue: Device Profiles are currently an approximation because they use the Windows Scalability Group. Epic indicates this will be fixed in a future release.

Input Trigger Device Updates (Mobile)

Creators can now:

This is especially relevant for shooters, tycoons, RPGs, and puzzle games that depend on reliable touch UX.

Performance Tooling: Spatial Profiler and Memory Diagnostics

Spatial Profiler Improvements

Epic improves Spatial Profiler usability and reporting:

New Fortnite Tools for Memory Diagnostics

Two new tools target common performance pitfalls:

You can find these under Fortnite Tools via Select Mode.

Physics Toolset Expansion: Verse API, Add Physics Tool, Chaos Visual Debugger

UEFN physics keeps maturing in v39.00 with three major upgrades.

New Physics Verse API

New Verse functions for fort_character and creative_prop enable more advanced physics interactions:

Epic recommends checking the Verse API Reference for full details.

New Add Physics Tool

Fortnite Tools gains an Add Physics tool for batch workflows:

For large islands, this is a practical productivity win.

Chaos Visual Debugger Enabled (CVD)

CVD is now enabled for UEFN development, supporting capture, replay, and inspection of:

You can access it via Tools > Debug > Chaos Visual Debugger.

This is especially valuable for investigating unexpected query results, collision behavior, and physics geometry complexity.

AI & NPC Control: New Scene Graph Components for Behaviors

Epic introduces a major update for NPC control in Verse by shifting key capabilities into Scene Graph components attached to NPC entities.

New components include:

This creates a more granular, scalable foundation for reactive AI systems.

Debug Commands Additions

v39.00 adds more Beta Debug Commands:

Discover Changes: Social Play Signals and Variety Improvements

Epic updates Discover ranking models with a stronger emphasis on social play:

Epic is also testing new rows that highlight social islands, improving viral detection and social graph systems.

In addition:

Creators should review the updated How Discover Works documentation for the most accurate guidance.

Epic’s Picks: Attribution Requirement Begins in v39.00

Starting with v39.00, islands submitted to Epic’s Picks must include attributions on their island code.

This is a procedural requirement—treat it as a gate.

XP Tag Removed from Discover

Epic removes the XP tag because it didn’t clearly communicate what (beyond playtime) was awarding XP.

Pacific Break Content Update: Chapter Seven Assets and Items

v39.00 brings a major content drop: Chapter Seven: Pacific Break assets arrive in UEFN and Creative.

Devices

DBNO Device Updates

Down But Not Out device gains new options including:

Art Content: New Galleries Across POIs

New galleries cover Pacific Break locations:

Plus gameplay-oriented props like Ferris Wheel, Water Slide, Water Jet, and Water Innertubes.

Items and Weapons

Items:

New weapons:

Weapon improvements for CH7S1 include ADS while reloading/in air, checkpoint reload, aimpoint recoil, and more. Updated versions of some unvaulted weapons are also included.

New Documentation: Device Design Examples

Epic adds new design example docs for:

These are useful for onboarding, narrative, and moment-to-moment engagement design.

Community Bug Fixes and Platform Fixes

v39.00 includes multiple community-driven fixes spanning:

Known Issues to Track

Epic lists several known issues creators should plan around, including:

Scene Graph note: Scene Events remain effectively experimental due to a Live Edit session failure risk; Epic provides guidance to remove specific references if impacted.

What Creators Should Do Next

If you’re building for 2026, v39.00 sets clear priorities:

  1. Prepare for Jan 9, 2026: finalize in-island transactions design, validation, and disclosures.
  2. Migrate analytics before Dec 10, 2025 and set up Creator Portal reporting workflows.
  3. Adopt Mobile Preview and audit touch UX using Input Trigger updates.
  4. Use the new memory tools (Optimize Texture / Optimize Static Mesh) and Spatial Profiler improvements.
  5. Level up physics debugging with Add Physics and Chaos Visual Debugger.
  6. Update compliance workflows: attributions for Epic’s Picks, new disclosure rules, and the Fortnite Developer Agreement.

For full release notes, implementation steps, and rule details, readers should consult Epic’s official v39.00 documentation : 39.00 Fortnite Ecosystem Updates and Release Notes

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