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Prime95

Free#18 of 26 in Hardware Diagnostic SoftwarePC Stress Testing Tools PC Overclocking Software

Prime95: A free, cross-platform tool for CPU, cache, and multi-core stability testing. Ranked #18 of 26 in Hardware Diagnostic Software by our editors (6.7/10); pricing: Free plan; best for free cross-platform CPU stress testing.

6.7/10Editor score

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At a glance

Editor score
6.7 / 10
Pricing
Free plan
Best for
Free cross-platform CPU stress testing
Free plan
Yes
Paid from
Free
Stress testing
Yes
Founded
1996
Facts checked
20 Sep 2026

Where it wins
- Free on Windows, macOS, and Linux
- Tests CPU, cache, and multiple cores under high load
- Supports resource limits and PrimeNet work management
Where it doesn't
- Focuses on CPU workloads rather than GPU testing
- Does not cover storage testing
- Does not provide diagnostic reporting

Our verdict on Prime95

Prime95 is free software for CPU stress testing, computer stability testing, and distributed Mersenne-prime research. Its torture-test mode applies heavy workloads across multiple CPU cores and can test CPU and L1, L2, and L3 cache stability. It is suited to users checking processor behavior, cooling, or overclocking-related stability on Windows, macOS, or Linux, as well as participants in distributed primality testing and factoring projects.

Its strongest fit is focused CPU validation. Prime95 supports multi-core high-load testing, resource usage limits, Mersenne-prime primality testing, PRP tests with proofs and error checking, and P-1 and ECM factoring workloads. PrimeNet adds work assignment and computer management for distributed workloads. This combination gives the software more depth than a simple load generator, particularly for users who want verifiable computational work alongside stress testing. It remains narrowly focused, however, rather than serving as a broad hardware diagnostic suite.

Prime95 should be considered when free, cross-platform CPU and cache stress testing is the priority. Its Windows, macOS, and Linux availability makes it practical across common desktop operating systems, while resource limits provide control over workload usage. Users looking for dedicated memory, storage, or GPU testing, or for diagnostic reporting across several hardware categories, should choose a more specialized alternative. Prime95 is therefore a strong match for processor stability checks and distributed computational workloads, but not for end-to-end hardware diagnosis.

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Prime95 pricing

Plans Free planFree Free to use — no paid tier required for the core job.

See plans on mersenne.org

Prime95 fact sheet

Free plan	Yes
Paid from	Free
Platform support	Multi-platform
Stress testing	Yes
Memory testing	Not verified
Disk health checks	Not verified
GPU testing	Not verified
Bootable diagnostic media	Not verified
Diagnostic reports	Not verified
Deployment	Desktop
Platforms	Windows, macOS, Linux
Support	Community, Docs
Built for	Solo, Small business, Mid-market (editorial estimate)
Pricing	Free plan
Website	mersenne.org
Facts checked	20 Sep 2026

Alternatives to Prime95

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Also Ranked In

Prime95 is ranked in 3 of our directories.

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Featured on iTechGuides

Prime95 is listed in our Hardware Diagnostic Software directory. Add the badge to your site — it links back to this page.

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Guides on hardware diagnostic software

Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

Advertiser disclosure: iTechGuides is reader-supported. Vendors can pay for top positions in our rankings and for a place on other products' pages, and we may earn a commission when you click some links. Bought places stand at the number bought; this page and our disclosure say so. Paying vendors may get a fuller, more detailed review from our editors, and that review can change their score. How we rank.

Last updated 7 Oct 2026 · How we research and update