Yosys
Framework for Verilog RTL synthesis that turns hardware designs into gate level netlists for ASIC cell libraries and FPGAs, and serves as a formal verification front end.
What it does and how it connects
Yosys is a framework for Verilog RTL synthesis that turns hardware designs into gate-level netlists for ASIC cell libraries and FPGAs, and serves as a formal verification front end. It has extensive Verilog-2005 support and a set of synthesis passes that can be combined with synthesis scripts or extended in C++.
It converts Verilog to BLIF, EDIF, BTOR, SMT-LIB, and simple RTL Verilog, maps to ASIC standard cell libraries in Liberty format and to Xilinx 7-Series and Lattice iCE40 and ECP5 FPGAs, and includes built-in formal methods for checking properties and equivalence. It also serves as the back end for formal tools such as sby for SMT-solver-based property checking and mcy for mutation coverage.
Yosys is free software licensed under the ISC license, and the latest release at research time is v0.70.
What engineers report
Since #6447 (fix for #6409), verific -import no longer connects the output ports of blackbox cell instances.
2026-11-05Read the original
Alternatives
Compare side by side- Verilator
Verilator is an open-source Verilog and SystemVerilog simulator and linter that compiles designs into fast C++ or SystemC models.
- OpenLane
OpenLane 2 is an infrastructure library for building digital ASIC implementation flows from RTL to GDSII, rather than a synthesis framework.
- KLayout
KLayout is a layout viewer and editor for chip mask layouts in GDS and OASIS formats, rather than an RTL synthesis framework.
- ngspice
ngspice is the open-source SPICE simulator for analog, digital, and mixed-signal circuits, driven by netlists and the command line.
Recurring errors it addresses
Error Index entries this tool is built to reduce or work around.
Sources
Not verified
- Pricing: none stated on the vendor site or repo as read.
Last verified November 6, 2026. Listings are informational. The evidence score measures public, verifiable evidence and is not an endorsement or a compatibility claim.