jscpd Performance Comparison: v4 (TypeScript) vs v5 (Rust)

June 13, 2026 · View on GitHub

Date: 2026-06-08
Runs per configuration: 10 (fixtures, svelte), 3 (CopilotKit)
Machine: macOS (Apple Silicon)

Versions

Tool	Version	Runtime
jscpd v4	4.2.5	Node.js
jscpd v5 (cpd)	5.0.4	Native binary (Rust)

Target	Files	Size	Description
fixtures	548	1.5 MB	Multi-language test fixtures (126+ formats)
svelte	8,963	38 MB	Svelte framework source code
CopilotKit	17,092	159 MB	Large real-world TypeScript/React project

Metric	jscpd v4	jscpd v5	Speedup
Mean real time	1.030s	0.030s	34.3x
Std dev	0.042s	0.000s
Min	1.000s	0.030s
Max	1.130s	0.030s
Mean user time	1.174s	0.085s
Mean sys time	0.074s	0.050s

Metric	jscpd v4	jscpd v5	Speedup
Mean real time	15.803s	0.428s	36.9x
Std dev	1.010s	0.021s
Min	14.740s	0.390s
Max	17.790s	0.450s
Mean user time	16.075s	0.553s
Mean sys time	0.738s	1.110s

Metric	jscpd v4	jscpd v5	Speedup
Mean real time	82.890s	3.440s	24.1x
Std dev	4.086s	0.699s
Min	79.560s	2.900s
Max	87.450s	4.230s
Mean user time	100.020s	7.323s
Mean sys time	18.263s	3.100s

Metric	jscpd v4	jscpd v5
Files analyzed	13,944	12,386
Clones found	12,272	22,487

Run	Real (s)	User (s)	Sys (s)
1	1.13	1.17	0.10
2	1.00	1.15	0.07
3	1.01	1.16	0.07
4	1.01	1.17	0.07
5	1.00	1.16	0.07
6	1.01	1.17	0.07
7	1.01	1.17	0.07
8	1.02	1.19	0.07
9	1.03	1.20	0.07
10	1.08	1.20	0.08

Run	Real (s)	User (s)	Sys (s)
1	0.03	0.08	0.05
2	0.03	0.09	0.05
3	0.03	0.08	0.05
4	0.03	0.08	0.05
5	0.03	0.08	0.05
6	0.03	0.09	0.06
7	0.03	0.09	0.04
8	0.03	0.09	0.05
9	0.03	0.08	0.05
10	0.03	0.09	0.05

Run	Real (s)	User (s)	Sys (s)
1	15.98	16.06	0.70
2	15.06	15.55	0.59
3	14.74	15.35	0.56
4	17.37	16.03	1.04
5	17.79	17.54	1.38
6	15.86	16.00	0.72
7	15.11	15.67	0.63
8	15.28	15.89	0.60
9	15.47	15.99	0.59
10	15.37	16.67	0.57

Run	Real (s)	User (s)	Sys (s)
1	0.39	0.55	0.96
2	0.43	0.55	1.23
3	0.40	0.55	0.95
4	0.41	0.54	1.18
5	0.45	0.56	1.11
6	0.45	0.56	1.20
7	0.44	0.56	1.19
8	0.44	0.55	1.17
9	0.43	0.56	0.97
10	0.44	0.55	1.14

Run	Real (s)	User (s)	Sys (s)
1	87.45	99.76	20.15
2	79.56	97.08	16.02
3	81.66	103.22	18.62

Run	Real (s)	User (s)	Sys (s)
1	2.90	7.41	3.13
2	4.23	7.16	3.18
3	3.19	7.40	2.99

After correcting the benchmark methodology, v5 is consistently 24–37x faster than v4:

Target	v4 (TypeScript)	v5 (Rust)	Speedup
fixtures (548 files, 1.5 MB)	1.03s	0.03s	34.3x
svelte (9K files, 38 MB)	15.80s	0.43s	36.9x
CopilotKit (17K files, 159 MB)	82.89s	3.44s	24.1x

Startup overhead: v5's native binary has near-zero startup cost. v4's Node.js runtime adds ~1s even for tiny fixtures.
Scaling: v5 scales well from small to large codebases. CopilotKit (159 MB) takes only 3.4s. v4 takes 83s on the same target.
CPU utilization: v5's higher user time relative to real time (e.g., CopilotKit: 7.3s user vs 3.4s real) shows effective multi-threading. v4 is single-threaded (user ≈ real).
Consistency: v5 has tighter variance across all runs. On CopilotKit, v5's std dev is 0.7s (20% of mean) vs v4's 4.1s (5% of mean, but absolute variation is much larger).
File scanning differences: v4 with --no-gitignore analyzes more files than v5 on svelte (11,672 vs 4,322) because v5's gitignore handling differs. This means v5 is even more efficient per-file analyzed than the raw speedup numbers suggest.
Detection accuracy: v5 finds more clones on large codebases (1,055 vs 903 on svelte, 22,487 vs 12,272 on CopilotKit), likely due to different token counting and the maxSize default behavior.