Benchmarks

BUI is fast where it matters to people: it opens quickly, it sits at zero CPU while you’re not touching it, and it stays smooth when thousands of things move. Here are the numbers, with everything you need to judge them.

Start time and battery

What was measured: the same small settings window (a label, a text field, a checkbox, a slider and a button), written each of the five ways, from bench/apps. Each ran on BUI’s CPU renderer (the default) and on its GPU renderer (BUI_GPU=1).

The last rows are one gpui-syntax source file, settings.rs, compiled unchanged against blenderui, Zed’s gpui and gpui-fast. gpui has no form widgets, so there the controls are styled divs.

How: the median of 10 launches, from process start until the first frame is on screen, with Python 3.14 and Node 22.

• CPU renderer
• GPU renderer

• RustHTML + CSS
  • CPU renderer: 38 ms
  • GPU renderer: 42 ms
• JavaScriptReact, Node.js
  • CPU renderer: 94 ms
  • GPU renderer: 99 ms
• Blender componentsPython
  • CPU renderer: 112 ms
  • GPU renderer: 116 ms
• tkinter syntaxPython
  • CPU renderer: 139 ms
  • GPU renderer: 159 ms
• Qt syntaxPython
  • CPU renderer: 156 ms
  • GPU renderer: 161 ms

Open benchClose benchRyzen 7 5800U laptop, Windows 11, on AC power

Start time and battery: the same small settings window, median of 10 launches, process start to first frame

App	Renderer	Start time	CPU used to start	Memory (idle)	Idle CPU per minute
Rust (HTML + CSS)	CPU	38 ms	27 ms	13 MB	0 ms
	GPU	42 ms	61 ms	31 MB	1.8 ms
JavaScript (React, Node.js)	CPU	94 ms	100 ms	48 MB	68 ms
	GPU	99 ms	131 ms	60 MB	71 ms
Blender components (Python)	CPU	112 ms	86 ms	23 MB	0 ms
	GPU	116 ms	125 ms	32 MB	1.7 ms
tkinter syntax (Python)	CPU	139 ms	112 ms	25 MB	0.2 ms
	GPU	159 ms	157 ms	43 MB	2.4 ms
Qt syntax (Python)	CPU	156 ms	123 ms	27 MB	0 ms
	GPU	161 ms	160 ms	36 MB	1.2 ms
Same gpui code: blenderui	CPU	40 ms	27 ms	15 MB	0 ms
blenderui	GPU	43 ms	60 ms	31 MB	2.1 ms
gpui	GPU	231 ms	226 ms	29 MB	743 ms
gpui-fast	GPU	226 ms	217 ms	31 MB	2.5 ms

Python 3.14 and Node 22. The last rows are one gpui-syntax source file (bindings/rust/bench/common/settings.rs) compiled unchanged against blenderui, gpui and gpui-fast; gpui has no form widgets, so there the controls are styled divs. Battery cost is the CPU time an app causes; memory doesn't count GPU memory.

Source: README.md#performance · Ryzen 7 5800U laptop, Windows 11, on AC power

What it means:

• On the same code, blenderui shows its first frame about 5× sooner than gpui and gpui-fast, spends about 8× less CPU getting there, and on the CPU renderer uses half the memory.
• Idle, gpui keeps about 1.2% of a core busy. blenderui uses none.
• The GPU renderer starts a little slower and uses more memory (the GPU device). It pays off on large, animated scenes, below.

• BUI
• Others

• blenderuiCPU renderer40 ms
• blenderuiGPU renderer43 ms
• gpui-fastGPU226 ms5.7× more
• gpuiZed's, GPU231 ms5.8× more

Open benchClose benchRyzen 7 5800U laptop, Windows 11, on AC power

Start time, the same gpui-syntax file (bindings/rust/bench/common/settings.rs) compiled against each library: median of 10 launches, process start to first frame

Same gpui code	Renderer	Start time	CPU used to start	Memory (idle)	Idle CPU per minute
blenderui	CPU	40 ms	27 ms	15 MB	0 ms
blenderui	GPU	43 ms	60 ms	31 MB	2.1 ms
gpui	GPU	231 ms	226 ms	29 MB	743 ms
gpui-fast	GPU	226 ms	217 ms	31 MB	2.5 ms

gpui has no form widgets, so there the controls are styled divs. Memory doesn't count GPU memory.

Source: README.md#performance · Ryzen 7 5800U laptop, Windows 11, on AC power

• BUI
• Others

• blenderuiCPU renderer0 ms
• blenderuiGPU renderer2.1 ms
• gpui-fastGPU2.5 ms1.2× more
• gpuiZed's, GPU743 ms354× more

Open benchClose benchRyzen 7 5800U laptop, Windows 11, on AC power

Start time, the same gpui-syntax file (bindings/rust/bench/common/settings.rs) compiled against each library: median of 10 launches, process start to first frame

Same gpui code	Renderer	Start time	CPU used to start	Memory (idle)	Idle CPU per minute
blenderui	CPU	40 ms	27 ms	15 MB	0 ms
blenderui	GPU	43 ms	60 ms	31 MB	2.1 ms
gpui	GPU	231 ms	226 ms	29 MB	743 ms
gpui-fast	GPU	226 ms	217 ms	31 MB	2.5 ms

gpui has no form widgets, so there the controls are styled divs. Memory doesn't count GPU memory.

Source: README.md#performance · Ryzen 7 5800U laptop, Windows 11, on AC power

How battery cost is measured: laptops can’t report energy per app, so the benchmark uses CPU time as a proxy. It counts the CPU an app spends starting up, and the CPU it uses over 20 seconds while the window sits idle: that’s what drains a battery while an app is open. BUI redraws only when something changes and otherwise sleeps, so idle use is near zero on either renderer.

Fine print: Node’s event loop accounts for the JavaScript idle figure. Python’s times include starting the interpreter. Memory doesn’t count GPU memory.

Frame times

What was measured: the full Blender components demo (520×900), from Python and C.

• Complete frameeverything redrawn~0.7 ms
• Input to screennative window~0.06 ms
• Hover or scrubdamage only~0.05 ms

Open benchClose benchRyzen 7 5800U laptop, Windows 11, on AC power

Python and C, the full component demo (520×900)

Frame	Time
Complete frame (everything redrawn)	~0.7 ms
Hover or number-scrub frame (damage only)	~0.05 ms
Native window: input event → on screen	~0.06 ms

Dear ImGui's demo window with every section open (27k triangles, 1280×800) is a full software redraw of about 5–8 ms.

Source: README.md#performance · Ryzen 7 5800U laptop, Windows 11, on AC power

Rust against gpui and gpui-fast

What was measured: a 1000×800 window filled with N rounded, numbered cells, built with the same element tree in every framework. In this table, every cell changes every frame (the worst case), with 3,000 cells. All apps ran in the same session.

• BUI
• Others

• blenderuiGPU renderer59.9 fps
• blenderuiCPU renderer57.6 fps
• gpui-fast31.5 fps1.9× fewer
• gpui19.9 fps3× fewer

Open benchClose benchRyzen 7 5800U laptop, Windows 11, on AC power

Rust, 3000 animated cells, all apps in the same session

	blenderui (GPU)	blenderui (CPU)	gpui-fast	gpui
FPS	59.9	57.6	31.5	19.9
CPU per frame	11.6 ms	22.0 ms	31.9 ms + GPU	50.5 ms + GPU
RAM	40 MB	30 MB	65 MB	77 MB
First frame	~5 ms	~5 ms	~200 ms	~220 ms
Idle CPU	0 %	0–0.9 %	0–0.4 %	0.9–1.4 %

gpui-fast's heavy-scene frame rate varies between sessions on this laptop (30–60 fps), so compare within one session.

Source: README.md#performance · Ryzen 7 5800U laptop, Windows 11, on AC power

• BUI
• Others

• blenderuiGPU renderer11.6 ms
• blenderuiCPU renderer22.0 ms
• gpui-fast31.9 ms + GPU2.8× more
• gpui50.5 ms + GPU4.4× more

Open benchClose benchRyzen 7 5800U laptop, Windows 11, on AC power

Rust, 3000 animated cells, all apps in the same session

	blenderui (GPU)	blenderui (CPU)	gpui-fast	gpui
FPS	59.9	57.6	31.5	19.9
CPU per frame	11.6 ms	22.0 ms	31.9 ms + GPU	50.5 ms + GPU
RAM	40 MB	30 MB	65 MB	77 MB
First frame	~5 ms	~5 ms	~200 ms	~220 ms
Idle CPU	0 %	0–0.9 %	0–0.4 %	0.9–1.4 %

gpui-fast's heavy-scene frame rate varies between sessions on this laptop (30–60 fps), so compare within one session.

Source: README.md#performance · Ryzen 7 5800U laptop, Windows 11, on AC power

More results, at 100 and 1,000 cells:

• blenderui GPU
• blenderui CPU

Open benchClose benchRyzen 7 5800U laptop, Windows 11, on AC power

Rust, full results: 100, 1000 and 3000 animated cells

	blenderui (GPU)	blenderui (CPU)	gpui-fast	gpui
FPS, 1000 animated cells	60	60	49.2	36.4
CPU per frame, 1000 / 100 cells	4.7 / 1.2 ms	10.2 / 4.6 ms	20.5 / 2.7 ms + GPU	27.7 / 4.7 ms + GPU
Uncapped FPS, 100 / 1000 / 3000 cells	1491 / 309 / 94	649 / 202 / 76	-	-
RAM, 1000 / 100 cells	35 / 28 MB	24 / 21 MB	45 / 47 MB	47 / 40 MB
GPU memory	19–22 MB	none	19–24 MB	16–21 MB

The GPU renderer is off by default: Application::new().gpu(true), tk.Tk(gpu=True), bui.set_gpu(True) or BUI_GPU=1. Its shaders evaluate the software raster's formulas: 10 of 172,800 pixels differ by more than 3/255.

Source: README.md#performance · Ryzen 7 5800U laptop, Windows 11, on AC power

What it means:

• The GPU renderer beats gpui-fast on every measurement. It uses 2.2× less CPU per frame at 100 cells, 4.4× less at 1,000 and 2.8× less at 3,000, where it also runs at nearly twice the frame rate. It uses less RAM and the same GPU memory.
• The GPU renderer halves blenderui’s own CPU cost (22.0 to 11.6 ms at 3,000 cells). What stays on the CPU is the Rust side: cascade, layout and the paint list.
• The CPU raster stays the lightest on memory and remains the default.

How: each app measures its own CPU cycles across all threads (Windows’ QueryProcessCycleTime), its frames and its memory, over a 10-second window after a 3-second warm-up. The runner adds GPU utilisation and GPU memory from Windows’ performance counters, because GPU work isn’t process CPU time. “+ GPU” means gpui’s numbers exclude its GPU work, so read them with the GPU columns in the full results.

Fine print: one laptop, one 60 Hz display (which caps every app), an integrated GPU.

JavaScript and React

Startup

What was measured: a small React app (a counter) that quits as soon as its first frame is on screen. Each figure is the median of 12 launches after a warm-up launch (node bench/startup.js).

• QuickJS executablebui build68 ms
• Bun executablebui build --bun79 ms
• Bunbun app.js80 ms
• Node.jsnode app.js108 ms

Open benchClose benchRyzen 7 5800U laptop, Windows 11, on AC power

JavaScript startup: a small React app that quits after its first frame, median of 12 launches after a warm-up

	First frame	Launch to exit	RAM at first frame	What you ship
QuickJS executable (bui build)	68 ms	104 ms	19 MB	4.9 MB
Bun executable (bui build --bun)	79 ms	147 ms	35 MB	114 MB
Bun (bun app.js)	80 ms	152 ms	35 MB	Bun + your app
Node.js (node app.js)	108 ms	187 ms	45 MB	Node + your app
Rust (for reference: the benchmark app)	5 ms	~92 ms		3.5 MB

First frame is measured from the runtime's start. Launch to exit is wall time measured from outside, including process creation and teardown.

Source: README.md#performance · Ryzen 7 5800U laptop, Windows 11, on AC power

Animation

What was measured: the same scene as the Rust table, in one mode: one cell changes per frame, like a hover or a ticking value. GPU renderer, medians of 3 runs, React’s production build. CPU is the whole process, counted with the cycle counter as for Rust.

• Plain JS uses @blender-ui/native.
• React with signals passes the changing values as signals, so the grid renders once.
• React with state re-renders the grid every frame.

• Plain JS
• React + signals
• React + state

• QuickJS
  • Plain JS: 16.3 ms
  • React + signals: 14.9 ms
  • React + state: 51 ms
• Bun 1.4
  • Plain JS: 13.1 ms
  • React + signals: 13.3 ms
  • React + state: 20.8 ms
• Node 22
  • Plain JS: 14.4 ms
  • React + signals: 14 ms
  • React + state: 18.9 ms

Open benchClose benchRyzen 7 5800U laptop, Windows 11, on AC power

JavaScript animation, 3,000 cells: one cell changes per frame, GPU renderer, medians of 3 runs

3,000 cells	FPS	CPU per frame	RAM
Rust	59.6	12.0 ms	43 MB
QuickJS: plain JS / React with signals / React with state	59.1 / 58.7 / 19.7	16.3 / 14.9 / 51.0 ms	56 / 61 / 67 MB
Bun 1.4: plain JS / React with signals / React with state	58.8 / 58.4 / 55.8	13.1 / 13.3 / 20.8 ms	80 / 85 / 118 MB
Node 22: plain JS / React with signals / React with state	55.8 / 56.7 / 54.8	14.4 / 14.0 / 18.9 ms	88 / 93 / 121 MB

Plain JS uses @blender-ui/native; React with signals renders the grid once; React with state re-renders it every frame. React's production build throughout.

Source: README.md#performance · Ryzen 7 5800U laptop, Windows 11, on AC power

What it means:

• JavaScript costs little over Rust: 0.4–2.4 ms per frame, for sending changes to BUI’s UI thread.
• Signals make React as cheap as the plain API: the component doesn’t re-render.
• QuickJS starts fastest and uses the least memory, from a 5 MB file. It has no JIT, so re-rendering a 3,000-element list every frame drops it to 20 FPS. Keep big lists on signals, or build with --bun.

Next steps