What if your latest bluescreen was due to a hardware failure ?

OCCT is the most popular CPU/GPU/Power Supply testing tool available. OCCT is great at generating heavy loads on your components, and aims at detecting hardware errors or overclocking issues faster than anything else. A monitoring engine is also embedded, to ease diagnostic and see how your computer reacts under heavy load using graphs.

OCCT is free for personal use only !

If you are running OCCT in a corporate or commercial environment, you have to buy a PRO license to use OCCT

I see an increasing number of companies downloading the free version of OCCT and shamelessly using it in their coporate environment. The free version of OCCT is meant to make OCCT as useful and widely used as possible. This has been the case since it started, back in 2003.

This time, when you do this, you aren't stealing from a big company !

OCCT isn't enough to make a living as of now (far from it). Please support me and participate in keeping the free edition... free for everyone !


OCCT's own CPU test. Small data set is great at pushing your CPU to its limits, and Large data set is the best at finding errors quickly


The famous Linpack test, known for pushing Intel CPUs to their limits. Not as great on AMD CPUs though, and less likely to pick up errors than OCCT


OCCT's version of the furry donut, which includes a error detection mode for finding rendering errors automatically


Exclusive OpenCL-based Memtest for testing your graphic card's memory ! Runs on any GPU (Intel, AMD, Nvidia) with OpenCL support. It is great at finding faulty bits, less at finding overclocking-induced errors


Combines CPU:OCCT and GPU:3D tests to stress your power supply and motherboard. This test is the most power-hungry included in OCCT. Useful to identify power-starved components !


OCCT will monitor your computer and present you real-time graphs showing you temperatures, voltages, fan speed, frequencies, component usage, and power comsumption during your tests.

Built-in protection for your computer

Worried about frying your components ? Turn the maximum temperature threshold in OCCT's options ! Should a component reach this critical temperature during a test, OCCT will stop itself immediately.

Test report

At the end of a test, you will be able to save a full graphical report of what happened during the test, for diagnostic purposes

Pricing Tables

OCCT hasn't gone fully commercial !
All features, except the test report in png format, are still available in the free version !

OCCT has been around since 2003, free to use except for professionnal users. This scheme worked to the extend of covering hosting costs, and purchasing license and test hardware for developing OCCT. However, at the time i write this, OCCT has not been making a penny for its authors.

To encourage everyone to participate in the OCCT adventure, we introduced a very cheap license system so that you can show your support to OCCT.

Please review the prices below and help us in developing OCCT !

1 Month


  • 5 Tests
  • Embedded Monitoring
  • Overheat protection
  • No waiting time

1 Year


  • 5 Tests
  • Embedded Monitoring
  • Overheat protection
  • No waiting time
  • Test Reports



  • 5 Tests
  • Embedded Monitoring
  • Overheat protection
  • No waiting time
  • Test Reports

Pro License


  • 5 Tests
  • Embedded Monitoring
  • Overheat protection
  • No waiting time
  • Test Reports
  • No Windows domain lock
  • CSV readings export


As OCCT was rewritten from scratch, we need kind souls to translate OCCT. Everyone that sends me a translation in a language not yet supported by OCCT will receive a Perpetual license for free !

How to translate OCCT

Translating OCCT is easy. First, download the english translation file : English.lang . Save it next to OCCT.exe and rename it to the language you're going to translate OCCT to.

Edit it using your favorite text editor ( i like Notepad++, but any will work - make sure you keep UTF-8 as the encoding though).

The first line says : <Language Name="English"> . Replace "English", obviously.

You'll then find the block for the language codes supported by this translation. Just list whichever language code applies to your translation. These are used by OCCT to automatically load your language file on startup, by matching this code with Windows's display language. For instance, here is the French language code list :


You'll find a list of language codes here. Look at the last column.

Then, it is just a matter of replacing every string by its translation. When you're done, start OCCT, and your translation will be available in the option menu (the gear icon). Test it, and send it to support@ocbase.com



Which test is the best at detecting hardware errors ?

CPU:OCCT, Large data set, with Auto number of threads is, hands-down, what will detect CPU/Memory/Motherboard stability issues faster. Use GPU:3D in fullscreen mode for GPU testing, GPU:Memtest for testing your Graphic card's Memory, and Power supply for testing your PSU. Most errors are detected within the first 5 minutes. However, i recommend doing at least a 1 hour long test just to be sure.

Which test puts the most stress on the CPU ?

If you have an Intel CPU, try the latest Linpack version available. OCCT's CPU Test with Small data set is the best on AMD CPUs, and a close second on Intel CPUs.

GPU:3D and furry donut based tests are Power virus

NO ! A Power virus is a stress test that you do not have control upon. This term was applied to OCCT's GPU test when we launched its first version, 10 years ago, by the marketing team of a certain brand of graphic card's manufacturer, when their shiny new graphic card could not withstand the test at all - it blackscreened instantly and required a reboot. This was due to a design failure of their reference design board. I don't know why the term sticked, despite being wrong. GPU:3D is a stability test just like the others.

Starting at how many errors do you consider a computer unstable ?

Seriously : One.

Do I have to purchase OCCT to know where the errors come from ?

No ! The Free version has always been designed to be usable "as is". OCCT isn't witholding information from you (I would call that stealing). It detects errors, but can't tell you where they come from. On the software point of view, it is as if it asked the for 2 + 2 and got 5 as an answer.

  • It is because the CPU miscalculated and answered that 2 + 2 = 5 ?
  • Is it because the memory stored a 3 instead of a 2 ?
  • Is it because when transferring the 2 from the memory to the CPU, the 2 got transformed to a 3 ?

As there's no sure way of reproducing the error that occured, there's no way of knowing what is going on. To further pinpoint errors, you have to dig yourself : lower the CPU frequency a notch and see if things are going better, up a voltage very carefully and see if it holds better... and pinpoint where the errors comes from. If you have access to spare parts, it is even easier to diagnose : replace and see what's going on.

I lost my license : how can I get it back ?

Send an email to support@ocbase.com and please give us at least a day for sending you your license back.

I am not using OCCT in a commercial or professionnal environment, yet my computer is joined to a windows domain. Can i run OCCT ?

Only the PRO version of OCCT will accept to launch on a computer joined to a windows domain. This is meant at detecting uses in professionnal and commercial environment, as they heavily rely on Windows domain. In the past, as there are enthousiasts that have a Windows domain at home, we offered a way of disabling this check as they were indeed not in a commercial environment, but this saw too much abuse. About 90% of the requests were from people trying to avoid the PRO license entirely. We thus removed that possibility, and you indeed need a PRO license now to run OCCT on a computer joined to a Windows domain.


Version 5.4.2
  • MAIN : Updated Authenticode signature ( SHA-1 and SHA-256 )
  • TRANSLATION : Updated Simplified chinese and Danish (Thanks !)
Version 5.4.1
  • MAIN : Added authenticode signature - When app has enough reputation, smartscreen warnings should go away !
Version 5.4.0
  • GPU:Memtest : First release ! An new OpenCL test that uses the same algorithm than memtest86 to test your GPU memory
  • UI : Reworked CPU, GPU and Power supply icons
  • UI : Fixed a display-issue only where OCCT displayed a license expired when it was still valid in the about window
  • TRANSLATION : Updated a lot of language files
Version 5.3.5
  • CPU:LINPACK : Fixed a bug where false positive could be reported in some (thankfully rare) cases
  • Translations : Updated Korean language (Thanks again JaeHyung)
Version 5.3.4
  • POWER SUPPLY : Fixed a bug where the selected instruction set wasn't properly saved
  • Translations : Fixed Korean language not appearing
  • Translations : Updated several translations
Version 5.3.3
  • CPU:OCCT : Added instruction set to test summary in the UI
  • CPU:LINPACK : Fixed a critical bug with Linpack parsing on CPUs with a huge number of cores - false positives were reported in some (thankfully rare) cases (Thanks Stephen !)
  • CPU:LINPACK : Improved test efficiency on CPU with lots of cores
  • CPU:LINPACK : Removed the ability to specify memory in percent, as between 1GB and 8GB is best
  • GPU:3D : No longer slows down when its window gets out of focus (Thanks SSateneth)
  • GPU:3D : Improved graphic card selection in multi-GPU configurations
  • GPU:3D : Fixed a crash when GPU:3D has more than 30 sensors to display
  • POWER SUPPLY : Switched to CPU:OCCT in small data set instead of Linpack
  • MONITORING : The max temperature threshold can now be disabled/enabled with a checkbox and is disabled by default
  • TESTING : Added a difference between "Cancelled" (triggers when a user closes GPU:3D's window for instance ) and "Crashed" (the test process terminated unexpectedly)
  • Translations : Added Danish (Thanks to Martin !)
  • Translations : Added Korean (Thanks to Jaehyung !)
Version 5.3.2
  • CPU:LINPACK : Fixed a critical bug with Linpack parsing on CPUs with a huge number of cores - false positives were reported in some (thankfully rare) cases (Thanks Stephen !)
Version 5.3.1
  • MONITORING : Huge update to the monitoring engine - better readings, newer CPU support
  • MONITORING : Updated how the default sensors are picked. New algorithm avoids selecting sensors with readings above max threshold for temperatures !
  • CPU:OCCT : Auto mode now disables AVX by default on AMD CPU in all data set sizes
  • MAIN : increased the waiting screen width to fit most translation in one line for looks
  • Translations : Added Japanese (Big thanks to Masao !)
  • Translations : Added Chinese (Simplified) (Thanks QMRQ ! )
  • Translations : Added Chinese (Traditional) (Thanks Danfong ! )
  • Translations : Added Swedish (Thanks Nilas ! )
Version 5.3.0
  • UI : Main window is now fully resizable
  • MONITORING : added Min/Max value colums in table view
  • MAIN : Improved license and .lang file detection speed
  • MAIN : Fixed a bug with some .net framework that are missing a particular registry function
  • MAIN : Fixed an issue where OCCT could crash at startup when no graphic card driver was installed
  • MAIN : Fixed a display bug with test durations over 24 hours
  • Translations : Fixed a bug where putting a corrupt English.lang file next to OCCT.exe could crash the app
Version 5.2.1
  • CPU:OCCT : fixed an issue where small data set might trigger an exception on some Ryzen CPUs
Version 5.2.0
  • CPU:OCCT : Huge update to the test
  • CPU:OCCT : Small data set is much more efficient and surpasses even Linpack
  • CPU:OCCT : Better support for high number of cores
  • CPU:OCCT : Much better AVX2 and AVX512 support
  • CPU:OCCT : User can select which AVX instruction set is used
  • CPU:OCCT : Updated CPU:OCCT's Auto rule for instruction sets to disable AVX in small data set for AMD CPUs
  • Translations : Added Dutch translation (Thanks Menno !)
  • Translations : Fixed an error where the included translation file in OCCT would take precedence over the one in a .lang file
Version 5.1.1
  • Generates simple crash reports when the main UI encounters an unexpected condition
Version 5.1.0
  • CPU:LINPACK : Better handling of "use logical cores" and simpler startup
  • CPU:LINPACK : Test is now more optimized optimized, Check it out !
  • GPU:3D DX11 : Test has undergone a huge update in this version
  • GPU:3D DX11 : Higher load on the GPU
  • GPU:3D DX11: FPS limit now works again
  • GPU:3D DX11 : added back sensor display
  • GPU:3D DX11 : Fixed mouse cursor displaying in fullscreen mode
  • GPU:3D DX11 : removed dependencies to old DLLs
  • GPU:3D DX11 : Fixed error detection algorithm on some Quadro GPU
  • GPU:3D DX11 : Fixed a rare bug where GPU:3D could fail to start
  • GPU:3D DX9 : Removed
  • UI : Fixed a few typos
  • UI : Number input checking much improved
  • UI : Fixed a bug where duration > 24 hours where not fully displayed in remaining time during a test
  • UI : Fixed a crash when right-clicking the title bar. Silly me.
  • UI : While OCCT is running, computer sleep (both screen and system) should be prevented
  • Translations : Removed unused strings and update to language files
  • Added Czech translation (Thanks Jaromir !)
  • Added German translation (Thanks Jürg !)
  • Added Italiano translation (Thanks Dendari ! )
  • Added Polski translation (Thanks Jaroslaw ! )
  • Added Romanian translation (Thanks Doruletz !)
  • Added Ukrainian translation (Thanks Arefiev !)
Version 5.0.1
  • Fixed an issue with CPU:OCCT small data set not performing as expected
  • Fixed an issue with CPU:OCCT not counting the cores properly in auto mode
  • Fixed a display issue with the number of cores used in CPU:LINPACK (it was a display issue only)
  • Fixed the overheating detection taking into account all sensor, not only enabled ones
  • Fixed the "Test progress" sentence not translating
  • Added Spanish language (Thanks German !)
  • Added Slovenian language (Thanks Jadran !)
  • Added Portugues language (Thanks Maxence and his girlfriend !)
  • Updated Russian language (Thanks Konorimci !)
Version 5.0.0
  • Complete UI rewrite ( material design )
  • Updated all tests to count the number of errors instead of stopping at the first one
  • Updated monitoring engine
  • Updated Linpack with a 2019 version
  • Reimplemented most things
  • Features are too numerous to be listed here - it is a complete reboot of the program