Arachne-pnr implements the place and route step of the hardware compilation process for FPGAs. It accepts as input a technology-mapped netlist in BLIF format, as output by the Yosys synthesis suite for example. It currently targets the Lattice Semiconductor iCE40 family of FPGAs. Its output is a textual bitstream representation for assembly by the IceStorm icepack command. The output of icepack is a binary bitstream which can be uploaded to a hardware device.

Together, Yosys, arachne-pnr and IceStorm provide an fully open-source Verilog-to-bistream tool chain for iCE40 1K and 8K FPGA development.

The authors of arachne-pnr have now prepared its successor 'nextpnr'.