Article

Performance

How Compose SwiftUI compares with plain SwiftUI.

Two benchmarks compare Compose SwiftUI with plain SwiftUI (release builds). Full results are in docs/bench/RESULTS.md.

50 screens, each written once in plain SwiftUI and once in Compose SwiftUI, reading the same Kotlin ViewModel (mean of per-screen medians). The SwiftUI version observes the whole screen state through one ObservableObject, the usual way to bridge a StateFlow in a KMP app:

	Pixel-identical	Mount: SwiftUI → Compose SwiftUI	Update: SwiftUI → Compose SwiftUI
iOS simulator	48 / 50	24.1 → 26.1 ms	1.92 → 1.48 ms
macOS	50 / 50	14.4 → 17.1 ms	2.11 → 2.07 ms

Scenarios that the 50 screens don't cover, against plain SwiftUI with native @Observable models (one object per row, so a change re-evaluates only the views that read it). iOS simulator, list rows with an icon, two lines of text and an unread dot, all pixel-identical (macOS results are in the full results):

	Plain SwiftUI	Compose SwiftUI, `LazyForEach`	Compose SwiftUI, Kotlin loop
10,000-row `List`: mount	23.5 ms	28.2 ms	818.8 ms
10,000 rows: one row changes	0.16 ms	0.41 ms	3.24 ms
10,000 rows: every row changes	4.0 ms	4.5 ms	78.5 ms
Scrolling, per page of rows	9.7 ms	13.8 ms	22.9 ms
60 bars, animated change: apply	5.1 ms	7.5 ms (same frame count, no hitches)	—

Updates of a regular screen are as fast as plain SwiftUI or faster, because only the views whose data changed re-render. Mounting costs 8% to 18% more, and a new row costs 40% (iOS) to 70% (macOS) more while scrolling: SwiftUI builds one type-erased view per node because the tree is built at runtime. For long lists, use LazyForEach: with a Kotlin loop, every row is composed and kept up to date even off screen.

iOS simulator: 50 screens

Pixel-identical (≤0.01% before and after 30 updates): 48 / 50
Mount (median per screen, then mean): SwiftUI 24.08 ms, Compose SwiftUI 26.06 ms (×1.08)
Update (state change → laid out): SwiftUI 1.915 ms, Compose SwiftUI 1.476 ms (×0.77)

#	Screen	diff	after updates	mount SwiftUI	mount Compose	update SwiftUI	update Compose
1	01 · Profile & settings	0.0000%	0.0000%	25.87	26.85	1.831	1.032
2	02 · Mail inbox	0.0000%	0.0000%	29.56	30.39	1.383	1.049
3	03 · Analytics dashboard	0.0000%	0.0000%	28.30	29.63	2.185	1.483
4	04 · Music player	0.0000%	0.0000%	12.93	14.25	1.090	0.717
5	05 · Weather	0.0281%	0.1333%	16.81	19.32	1.250	0.907
6	06 · Shopping cart	0.0000%	0.0000%	30.26	32.14	2.336	1.663
7	07 · Calendar agenda	0.0000%	0.0000%	18.25	21.93	1.628	1.430
8	08 · Chat conversation	0.0000%	0.0000%	16.03	17.21	1.244	0.696
9	09 · Sign-up form	0.0000%	0.0000%	41.05	42.31	4.601	1.484
10	10 · Preferences	0.0000%	0.0000%	41.24	43.44	6.229	6.710
11	11 · Photo grid	0.0000%	0.0000%	18.20	21.30	1.432	1.614
12	12 · Fitness activity	0.0000%	0.0000%	18.59	21.96	1.756	1.564
13	13 · Stocks watchlist	0.0000%	0.0000%	24.23	27.47	3.262	3.857
14	14 · News feed	0.0000%	0.0000%	15.65	17.29	0.915	0.989
15	15 · File browser	0.0000%	0.0000%	34.16	35.76	1.847	0.832
16	16 · Kanban board	0.0000%	0.0000%	27.05	31.04	2.469	2.359
17	17 · Recipe detail	0.0000%	0.0000%	19.59	21.20	1.558	1.418
18	18 · Banking	0.0000%	0.0000%	26.02	27.22	1.670	1.168
19	19 · Travel booking	0.0000%	0.0000%	24.17	25.85	1.492	1.045
20	20 · Contacts	0.0000%	0.2485%	39.32	39.45	2.467	1.033
21	21 · Notification center	0.0000%	0.0000%	17.47	19.53	1.244	0.778
22	22 · Map overview	0.0000%	0.0000%	14.09	15.00	1.299	1.283
23	23 · Bar chart report	0.0000%	0.0000%	16.29	17.79	1.462	1.201
24	24 · Pricing tiers	0.0000%	0.0000%	18.05	19.84	2.154	2.226
25	25 · Onboarding	0.0000%	0.0000%	11.69	11.50	2.255	1.160
26	26 · Leaderboard	0.0000%	0.0000%	30.47	31.96	1.979	1.719
27	27 · Order tracking	0.0000%	0.0000%	16.65	18.71	2.464	1.817
28	28 · Smart home	0.0000%	0.0000%	22.25	23.76	1.731	1.427
29	29 · Podcast episodes	0.0000%	0.0000%	26.63	28.13	2.191	1.736
30	30 · Pull request review	0.0000%	0.0000%	17.10	19.34	1.578	1.791
31	31 · Social profile	0.0000%	0.0000%	19.25	21.28	2.506	2.519
32	32 · Habit tracker	0.0000%	0.0000%	24.38	26.44	1.687	0.750
33	33 · Expense splitting	0.0000%	0.0000%	17.85	20.11	1.490	1.314
34	34 · Video library	0.0000%	0.0000%	29.38	34.14	1.136	0.832
35	35 · Online course	0.0000%	0.0000%	29.06	30.89	1.519	0.982
36	36 · Hotel detail	0.0000%	0.0000%	20.41	21.35	1.379	0.825
37	37 · Boarding pass	0.0000%	0.0000%	15.28	18.47	1.492	1.263
38	38 · Medication schedule	0.0000%	0.0000%	41.95	44.67	2.114	1.127
39	39 · Analytics table	0.0000%	0.0000%	18.06	18.59	1.390	1.146
40	40 · Restaurant menu	0.0000%	0.0000%	33.00	36.33	1.455	0.515
41	41 · Crypto wallet	0.0000%	0.0000%	29.75	32.73	2.120	2.009
42	42 · Task manager	0.0000%	0.0000%	27.01	27.79	1.424	0.968
43	43 · Event tickets	0.0000%	0.0000%	30.54	35.85	3.151	3.528
44	44 · Job listings	0.0000%	0.0000%	24.99	26.60	1.633	1.052
45	45 · Real-estate listing	0.0000%	0.0000%	17.59	18.38	1.485	1.151
46	46 · Sports scores	0.0000%	0.0000%	25.51	28.80	1.624	0.876
47	47 · Book library	0.0000%	0.0000%	19.28	22.35	1.536	0.671
48	48 · EV dashboard	0.0000%	0.0000%	31.69	31.49	1.881	1.390
49	49 · Sleep tracker	0.0000%	0.0000%	27.49	30.35	1.883	1.125
50	50 · System status	0.0000%	0.0000%	23.73	24.78	1.857	1.581

macOS: 50 screens

Pixel-identical (≤0.01% before and after 30 updates): 50 / 50
Mount (median per screen, then mean): SwiftUI 14.44 ms, Compose SwiftUI 17.06 ms (×1.18)
Update (state change → laid out): SwiftUI 2.108 ms, Compose SwiftUI 2.071 ms (×0.98)

#	Screen	diff	after updates	mount SwiftUI	mount Compose	update SwiftUI	update Compose
1	01 · Profile & settings	0.0000%	0.0000%	14.12	15.54	1.410	1.407
2	02 · Mail inbox	0.0000%	0.0000%	14.56	16.30	1.369	1.383
3	03 · Analytics dashboard	0.0000%	0.0000%	17.34	18.77	2.204	2.477
4	04 · Music player	0.0000%	0.0000%	8.74	10.15	1.151	1.093
5	05 · Weather	0.0000%	0.0000%	9.01	12.79	1.046	1.052
6	06 · Shopping cart	0.0000%	0.0000%	22.26	25.00	1.938	1.915
7	07 · Calendar agenda	0.0000%	0.0000%	11.26	15.89	1.923	2.306
8	08 · Chat conversation	0.0000%	0.0000%	7.95	9.87	1.484	1.040
9	09 · Sign-up form	0.0000%	0.0000%	29.63	31.20	4.235	4.589
10	10 · Preferences	0.0000%	0.0000%	35.19	37.36	8.566	9.906
11	11 · Photo grid	0.0000%	0.0000%	7.44	11.69	0.847	1.127
12	12 · Fitness activity	0.0000%	0.0000%	10.72	14.20	1.765	2.142
13	13 · Stocks watchlist	0.0000%	0.0000%	14.68	17.77	2.960	3.595
14	14 · News feed	0.0000%	0.0000%	8.83	11.10	0.877	1.169
15	15 · File browser	0.0000%	0.0000%	13.28	15.18	1.923	0.695
16	16 · Kanban board	0.0000%	0.0000%	16.76	20.17	1.851	2.071
17	17 · Recipe detail	0.0000%	0.0000%	12.20	14.23	2.145	2.381
18	18 · Banking	0.0000%	0.0000%	19.81	21.36	1.738	0.751
19	19 · Travel booking	0.0000%	0.0000%	14.63	16.93	2.109	2.159
20	20 · Contacts	0.0000%	0.0000%	26.13	30.26	4.074	2.552
21	21 · Notification center	0.0000%	0.0000%	8.98	11.01	1.157	0.956
22	22 · Map overview	0.0000%	0.0000%	7.52	10.43	1.237	1.564
23	23 · Bar chart report	0.0000%	0.0000%	9.13	10.97	2.043	2.196
24	24 · Pricing tiers	0.0000%	0.0000%	13.55	16.26	3.567	3.709
25	25 · Onboarding	0.0000%	0.0000%	5.65	7.17	1.791	1.686
26	26 · Leaderboard	0.0000%	0.0000%	16.00	19.60	1.874	1.205
27	27 · Order tracking	0.0000%	0.0000%	9.48	12.44	2.341	2.717
28	28 · Smart home	0.0000%	0.0000%	16.06	18.10	2.092	2.082
29	29 · Podcast episodes	0.0000%	0.0000%	17.35	19.63	2.623	2.011
30	30 · Pull request review	0.0000%	0.0000%	10.08	13.86	1.569	2.433
31	31 · Social profile	0.0000%	0.0000%	14.08	16.15	3.479	4.434
32	32 · Habit tracker	0.0000%	0.0000%	13.45	15.52	1.527	1.083
33	33 · Expense splitting	0.0000%	0.0000%	9.01	11.23	1.889	2.106
34	34 · Video library	0.0000%	0.0000%	14.22	19.20	1.466	1.357
35	35 · Online course	0.0000%	0.0000%	13.56	14.92	1.712	1.100
36	36 · Hotel detail	0.0000%	0.0000%	10.74	13.02	1.269	1.391
37	37 · Boarding pass	0.0000%	0.0000%	9.38	13.11	1.484	1.395
38	38 · Medication schedule	0.0000%	0.0000%	21.46	22.71	2.469	1.505
39	39 · Analytics table	0.0000%	0.0000%	10.56	12.22	1.888	2.083
40	40 · Restaurant menu	0.0000%	0.0000%	16.36	18.17	1.362	0.495
41	41 · Crypto wallet	0.0000%	0.0000%	18.05	19.58	2.919	2.900
42	42 · Task manager	0.0000%	0.0000%	20.45	23.43	1.772	1.275
43	43 · Event tickets	0.0000%	0.0000%	15.48	22.30	4.690	6.127
44	44 · Job listings	0.0000%	0.0000%	17.64	20.07	1.723	1.356
45	45 · Real-estate listing	0.0000%	0.0000%	9.96	11.92	1.816	1.830
46	46 · Sports scores	0.0000%	0.0000%	16.17	19.64	1.251	0.917
47	47 · Book library	0.0000%	0.0000%	12.55	16.26	0.962	0.929
48	48 · EV dashboard	0.0000%	0.0000%	21.03	22.01	2.114	2.258
49	49 · Sleep tracker	0.0000%	0.0000%	17.28	20.94	1.549	0.976
50	50 · System status	0.0000%	0.0000%	12.05	15.17	2.166	1.678

Scenarios: iOS simulator

scripts/run_scenarios.sh -sizes 1000,10000 [-lazy]. Plain SwiftUI uses native @Observable models (one object per row); Compose SwiftUI uses an immutable list in one Kotlin state, as a ViewModel would. Every case is pixel-identical. Mount is the median of three mounts after a warm-up; the other numbers are means over 30 one-row changes, 5 full updates and 60 scrolled pages.

Scenario	Plain SwiftUI	Compose SwiftUI, `LazyForEach`	Compose SwiftUI, Kotlin loop
1,000 rows: mount	23.85 ms	27.81 ms	55.90 ms
1,000 rows: one row changes	0.167 ms	0.157 ms	0.562 ms
1,000 rows: every row changes	1.90 ms	1.95 ms	9.02 ms
1,000 rows: scrolling, per page	9.94 ms	13.66 ms	20.20 ms
10,000 rows: mount	23.48 ms	28.24 ms	818.83 ms
10,000 rows: one row changes	0.160 ms	0.407 ms	3.240 ms
10,000 rows: every row changes	4.00 ms	4.52 ms	78.49 ms
10,000 rows: scrolling, per page	9.72 ms	13.77 ms	22.89 ms
60 animated bars: apply one change	5.12 ms	7.54 ms	—
60 animated bars: frames / hitches over 10 animations	254 / 0	254 / 0	—

Scenarios: macOS

Same scenarios in a 700×900 window. The frame sampler on macOS is a 120 Hz timer on the main run loop, so its hitch count is only indicative.

Scenario	Plain SwiftUI	Compose SwiftUI, `LazyForEach`	Compose SwiftUI, Kotlin loop
1,000 rows: mount	26.07 ms	36.98 ms	107.42 ms
1,000 rows: one row changes	0.189 ms	0.236 ms	0.691 ms
1,000 rows: every row changes	6.86 ms	7.19 ms	12.63 ms
1,000 rows: scrolling, per page	8.97 ms	14.64 ms	20.47 ms
10,000 rows: mount	26.46 ms	37.84 ms	1250.92 ms
10,000 rows: one row changes	0.137 ms	0.468 ms	3.249 ms
10,000 rows: every row changes	8.40 ms	8.95 ms	87.75 ms
10,000 rows: scrolling, per page	12.39 ms	20.95 ms	40.89 ms
60 animated bars: apply one change	4.40 ms	7.09 ms	—
60 animated bars: ticks / late ticks over 10 animations	506 / 3	515 / 8	—