TextMesh Pro Lag, CPU Spikes and GC Allocations: Causes and Fixes

Last reviewed October 31, 2026

Where the time goes in TextMesh Pro

• Whole-text rebuilds. Any new value re-parses the entire text and regenerates its mesh on the main thread before the canvas renders. Layout components ask for preferred sizes, which runs another measuring pass, and Auto Size lays the text out several times until it fits; together they can multiply the passes, as Unity's TMP developer explained on Android.
• Canvas rebuilds. A change to any element makes Unity re-analyze the whole canvas, so a ticking timer can rebuild a full HUD.
• Garbage. Building strings every frame allocates; Unity's memory guide points to TextMesh Pro's SetText overloads instead. Those still build a string in the Editor, and reading .text back after SetText allocates one.
• Glyphs added mid-frame. A character missing from a dynamic atlas is rasterized synchronously on the main thread when the text is parsed. Users report seconds of stalls for uncached Japanese text on low-end hardware, and the advice is to pre-bake static atlases per script.
• UI Toolkit. Its Advanced Text Generator, announced as the default in 6.5, comes with Unity reporting 10–40% lower CPU cost than its previous text, and Unity 6.6 adds allocation-free SetText overloads. It applies to UI Toolkit, not to uGUI and TextMesh Pro.

Unity's own mitigations still apply to any UI: split canvases by how often they change, avoid layout groups where anchors will do, turn off Raycast Target on text that is not clicked, and compute Auto Size once instead of every change.

How UniText keeps text cheap

• One batch per frame. A change marks the text dirty. Once per canvas update, before uGUI renders, every dirty text is processed in one pass, so several changes in a frame cost one rebuild.
• Worker threads. Parsing, shaping and layout of all changed texts run on a pool of worker threads, one fewer than the CPU cores, together with the main thread. Unity APIs are touched only on the main thread before and after the batch.
• Burst rasterization. New glyphs from all changed texts are collected together, rasterized by Burst jobs and uploaded before any mesh is built.
• Shaping caches. Repeated paragraphs skip shaping entirely, and paragraphs that reuse words, such as counters, timers and chat, splice cached words instead of shaping them again.
• No garbage from text. SetText takes a StringBuilder or a character span without allocating, and the rendered and markup-free text are read back without allocating.

readonly StringBuilder sb = new();

void Update()
{
    sb.Clear().Append("Score: ").Append(score);
    scoreText.SetText(sb);
}

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