Open source · GPL-3.0 · Rust
fastroute routes your board from a Specctra DSN file, like Freerouting — several times faster, without Java, and with the bugs fixed. It adds what real boards need: length matching, controlled impedance and differential pairs, with your KiCad design rules carried over.
Version 0.1.14 · Windows · macOS (Apple Silicon and Intel) · Linux (x64 and ARM64) · KiCad 7 or newer
fastroute--parity modefastroute started as a line-by-line port of Freerouting to Rust. With the Java router side by side, long-standing bugs became visible — and fixable.
.kicad_dru reach the router.New
Group the nets of a memory bus or a clock tree and fastroute adds serpentines after routing until they match. Every meander is checked for clearance before it is kept, so your board stays DRC-clean. Vias count with their stackup height, exactly as KiCad measures them.
From KiCad: a skew or length rule in your
board's custom rules is all it takes.
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USB, Ethernet and other pairs are routed first, with the second net following the first at the pair gap. They are held in place while the rest of the board is routed, and released only where the board cannot be completed otherwise. Intra-pair skew is matched afterwards.
From KiCad: a diff_pair_gap rule on your pairs.
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Tick Show the routing live in the web browser and a page opens next to KiCad with your board as it is routed: traces appear and get ripped up, airlines disappear one by one, and every pass reports how many connections are left. Hover a trace to see its net, click to highlight the whole net, switch layers on and off.
Stop on the page ends the run and keeps the best result so far. The page is served by fastroute on your computer — no internet, nothing to install — and the routing result is exactly the same with or without it.
Command line: fastroute -de board.dsn -do board.ses --live
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Tell the impedance tool what you need — RF=50, USB=90d — and
it computes the trace width for every layer from your board's stackup (microstrip,
stripline, differential), writes the DRC rules, and fastroute routes those nets at
full width, without necking down at the pins.
python3 impedance_cli.py board.kicad_pcb --class RF=50 --class USB=90d --write| Layer | Type | 50 Ω | 90 Ω diff |
|---|---|---|---|
| F.Cu | microstrip | 0.387 | 0.405 / 0.405 |
| In1.Cu | stripline | 0.297 | 0.227 / 0.227 |
| In2.Cu | stripline | 0.297 | 0.227 / 0.227 |
| B.Cu | microstrip | 0.387 | 0.405 / 0.405 |
Width (and pair gap) in mm for a common 1.6 mm 4-layer stackup (7628 prepreg), without solder mask.
Full pipeline (autorouter and optimizer) in exact mode, where fastroute produces the same result as Freerouting — so the times compare like for like.
| Freerouting (Java) | fastroute | fastroute + PGO | |
|---|---|---|---|
| Sum of 20 benchmark boards | 2102 s | 510 s | 420 s |
| DAC2020_bm01 | 960 s | 380 s | 310 s |
| CM5_MINIMA_3 | 410 s | 23 s | 20 s |
| Peak memory (typical) | 1–2 GB | 20–300 MB | |
The default parallel mode is another 1.5–3× faster on most boards, with results that no longer have to match Freerouting's.
KiCad demo boards, all tracks removed and routed again from scratch, then checked with KiCad 10's design rule checker. Numbers are unconnected items / routing violations.
| Board | Original design | Plain Freerouting flow | fastroute plugin |
|---|---|---|---|
| multichannel_mixer | 0 / 0 | 160 unrouted | 0 / 0 · 3.3 s |
| complex_hierarchy | 0 / 1 | 83 / 3 | 0 / 0 · 0.7 s |
| interf_u | 0 / 3 | 8 / 346 | 0 / 2 · 5.6 s |
| pic_programmer | 0 / 8 | 0 / 118 | 0 / 0 · 0.7 s |
| ecc83-pp | 0 / 0 | 0 / 6 | 0 / 0 · 0.3 s |
fastroute is distributed on GitHub. One package for every platform: the plugin picks the right fastroute binary itself — no Java, no Python packages, nothing else to install.
On the GitHub releases page, save
fastroute-kicad-<version>.zip (Windows, macOS and Linux in one file).
Do not unzip it — KiCad installs the zip file as it is.
In KiCad's main window (the project manager), click Plugin and Content Manager, or choose Tools → Plugin and Content Manager.
Click Install from File… at the bottom left, select the zip and confirm. fastroute now appears on the Installed tab.
Open the board in the PCB Editor. If it was already open, restart it or use Tools → External Plugins → Refresh Plugins. A fastroute button appears in the top toolbar.
Click the fastroute button, or Tools → External Plugins → fastroute autorouter. Choose a mode — Fast (default, parallel optimizer), Exact (Freerouting's result bit for bit) or Quick (router only) — and click Route. The window shows the progress (tick Show the routing live to watch the board in your browser); Stop keeps the best result so far. Tracks are imported and zones refilled when it finishes.
Run KiCad's DRC (Inspect → Design Rules Checker). Save your board before routing if you want to go back.
Net class widths and clearances, the minimum track width and the copper-to-edge clearance are used automatically. Rules in Board Setup → Custom Rules add more:
# match an SDRAM bus to 0.5 mm
(rule "SDRAM data"
(condition "A.NetName == '/SD_D*'")
(constraint skew (max 0.5mm)))
# route USB as a differential pair
(rule "USB"
(condition "A.inDiffPair('/USB_D')")
(constraint diff_pair_gap (opt 0.2mm)))The fastroute binary also runs on its own, on any Specctra DSN file:
# route, write the result to board.ses
fastroute -de board.dsn -do board.ses
# stop after 10 minutes, keep the best result
fastroute -de board.dsn -do board.ses --max-time=600
# watch it route in the browser
fastroute -de board.dsn -do board.ses --live
# Windows
fastroute.exe -de board.dsn -do board.ses
# all options
fastroute --helpStandalone binaries for every platform are on the
releases page.
Freerouting's options work as before (-mp, --router.*).
The binaries are not code-signed yet. On macOS and Linux the plugin sets them up by itself (executable bit, quarantine flag); nothing to do for you. Signing is one of the goals of the sponsorship.
fastroute is GPL-3.0, like Freerouting it is built on — all credit for the original routing algorithms goes to the Freerouting authors. Sponsorship pays for the time to test on more real boards, answer bug reports quickly, and sign the binaries for macOS and Windows.
A bug report with a board that shows the problem helps just as much.