Why Rider and ReSharper Were Slow to Start, and How Microsoft Helped Fix the Problem - The JetBrains Blog

JetBrains investigated reports that ReSharper’s out-of-process architecture, despite generally improving IDE responsiveness, caused unexpectedly slow cold starts on Windows because Microsoft Defender performed extensive scanning of its separate process, sometimes adding tens of seconds. Using Defender ETW logs and CPU-time measurements across repeated cold-start tests, the team found that IDEs and editor-class tools could face 10–40 seconds of scanning while Microsoft IDEs and command-line tools were typically scanned in under two seconds, with write-protected installation directories receiving more favorable scanning treatment. Collaboration with Microsoft clarified Defender’s behavior and led to Defender version 1.449.454.0 optimizations that improve ReSharper OOP and Rider performance when installed in write-protected paths, although JetBrains Toolbox’s user-writable installation location may still incur overhead that exclusions can partly reduce. JetBrains released its Defender Performance Tool on GitHub to help developers inspect real-time or recorded Defender scan activity, and recommends keeping Defender updated, using Microsoft’s performance-recording PowerShell tools, considering write-protected installation paths or approved exclusions, and using Dev Drives for repositories and package caches; ReSharper 2026.2.1 now enables OOP mode by default.

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