SZL is a technology that makes it possible to more quickly load and analyze large data files in Tecplot 360. SZL file format uses a .szplt file extension.

Benefits of Using SZL Technology

  • Faster to load, analyze & visualize results.
  • Less memory used when loading data.
  • Smaller files sizes.
  • MPI parallel writing capability.

SZL Technology reduces the amount of solution data loaded when analyzing CFD results. The technique involves breaking the grid into small pieces, called subzones, and reading in only the subzones needed. Feature extraction can then be performed on only those subzones. This method significantly speeds up loading and rendering data, as explained in Intelligently Defeating the I/O Bottleneck.

SZL technology allows tremendous speed ups in data transfer and reduces memory usage. It subdivides volume domains and loads only the data needed to create a plot.

Try Tecplot 360 for free

Performance Benchmarks

Platform: 183M cell CFD++ solution run on a Dell Precision laptop quad core with 16GB RAM
Tecplot Release File Type Time to First Image Peak Memory Usage File Size
Tecplot 360 2013 R1 PLT 27 seconds 14.6 GB 7 GB
Tecplot 360 2017 R1 SZL 3.7 seconds
7.3 times faster!
906 MB
93% less memory used!
3.5 GB
50% smaller file size!

Results depend on size, type and grid structure. Try it on your own data.

SZL Technology FAQs

Q: What is the first Tecplot release that includes SZL?

Tecplot 360 2014 R1 is the first release to include SZL. All subsequent Tecplot 360 releases include SZL. Versions released in 2013 and earlier do not have a SZL option. SZL file format has evolved over time and older versions of Tecplot 360 may not always read the more recent versions of SZL files.

Q: How to I generate SZL with my data?

SZL is included with your Tecplot 360 (2014 and later releases) installation. There are several ways to create SZL files:

  1. Use a simulation code that outputs SZL file format. See the list of solver codes.
  2. Use batch mode to read your data into Tecplot 360 and output in SZL file format. Watch the Preplot and SZL Convert Tools tutorial.
  3. Interactively use Tecplot 360 to read in your data and output in SZL file format. Follow this tutorial.

Download the most current version of Tecplot 360 (get a free trial) and try it with your own data!

Q: Does SZL have a parallel option?

Yes! In 2016, partitioned zones for finite-element (hexahedral and tetrahedral) zones was introduced and then extended to partitioned IJK-ordered zones. Tecplot’s MPI-based TecIO-MPI library allows you to output these zones types in parallel from your MPI-based solver. The TecIO-MPI library is installed with Tecplot 360. If you need TecIO-MPI for a different platform, you may obtain source code to compile on your machine. Learn more about the TecIO Library.

Q: What is the difference between PLT (.plt) and SZL (.szplt) file format?

Using SZL (.szplt) file format in Tecplot 360 dramatically speeds up data loading and analysis times, compared with using traditional PLT (.plt) file format. SZL Technology breaks the grid into small pieces called subzones. Only the subzones needed are read in, and feature extraction is performed on just those subzones. The technique is best explained in the Trillion Cell Challenge blog series. SZL files are also smaller than a PLT files for 3D finite-element data.

There is sometimes a tradeoff in output time between SZL and PLT file format. However, because finite-element (FE) files, are so much smaller, outputting SZL FE will be about the same as, or faster than, outputting PLT files. For ordered output, there would be no notable difference in output.

Q: Where can I get Technical Help?

Email our top tier Technical Support team at or call 425-653-9393.