- Settings → Telemetry Settings in F1 25.
- UDP Telemetry On · UDP Broadcast Mode Off · UDP IP Address
127.0.0.1· UDP Port20777. - UDP Format F1 25 or F1 25: 2026 Season Pack — StintLab reads both. Send rate 30 or 60 Hz for the finest traces.
- Nothing recording? StintLab's Help → Setup check says exactly what it can see and which setting to change.
The setup, step by step
This takes about a minute, and you only do it once — the game keeps its telemetry settings with the rest of its options.
- Open StintLab first.Start StintLab before or after the game — it listens for F1 telemetry on UDP port 20777 as soon as it is running. Its logo sits in the Windows tray; a grey badge means it is waiting for a game.
- In F1 25, open Settings → Telemetry Settings.The telemetry options live in the game's settings menu, under Telemetry Settings.
- Set UDP Telemetry to On and UDP Broadcast Mode to Off.Telemetry On makes the game send its data; Broadcast Off sends it to one address instead of every device on your network.
- Set UDP IP Address to 127.0.0.1 and UDP Port to 20777.127.0.0.1 is your own PC. 20777 is the game's default port and the one StintLab listens on.
- Set UDP Send Rate to 30 Hz or 60 Hz.Any rate records every lap; 30 Hz or more gives the finest traces at top speed.
- Set UDP Format to F1 25 or F1 25: 2026 Season Pack.StintLab reads both formats. If in doubt, choose F1 25.
- Drive one full lap, then open View → My laps.A lap is written the moment the game times it. If nothing appears, open Help → Setup check.
What each setting does
The Telemetry Settings menu is short, but every line matters. This is what each one does and what StintLab needs from it.
| Setting | Set it to | What it does |
|---|---|---|
| UDP Telemetry | On | Makes the game send its telemetry at all. Off by default — the single most common reason nothing is recorded. |
| UDP Broadcast Mode | Off | On sends every packet to every device on your network. StintLab runs on the same PC as the game, so it only needs the packets sent to one address. |
| UDP IP Address | 127.0.0.1 | Where the packets go. 127.0.0.1 means “this computer”, so the data never leaves your PC. |
| UDP Port | 20777 | Which door on that address. 20777 is the game's default and StintLab's. Change both together, never one. |
| UDP Send Rate | 30 or 60 Hz | How many times a second the game reports speed, pedals and position. Lap times are unaffected; trace detail is not — see below. |
| UDP Format | F1 25 or 2026 Season Pack | Which packet layout the game uses. StintLab reads these two. An older year's format, if your version offers one for last year's tools, is not read. |
You may also see a setting for whether your telemetry is public or restricted. That controls what other players' tools can see of your car in online sessions; StintLab reads your own car from your own game, so you can leave it as it is.
Which send rate: the one setting worth thinking about
The send rate does not change a single lap time — those come from the game's own timing, to the millisecond. It changes how finely each lap is drawn.
StintLab records a lap on a distance grid: it keeps a sample each time the car has moved at least 5 m since the last one, using whatever packets the game has sent. At high speed the packets themselves are the limit. At 300 km/h a car covers 83 m every second, so:
| Send rate | Car moves between packets at 300 km/h | StintLab sample spacing at 300 km/h |
|---|---|---|
| 10 Hz | 8.3 m | about 8.3 m — every packet |
| 20 Hz | 4.2 m | about 8.3 m — every second packet |
| 30 Hz | 2.8 m | about 5.6 m — every second packet |
| 60 Hz | 1.4 m | about 5.6 m — every fourth packet |
Two things follow. First, the difference only shows at speed: through a slow corner every rate fills the 5 m grid almost exactly. Second, where it shows, it matters — the start of a braking zone is at the top speed of the lap, and the brake point can only be placed as precisely as the samples around it. At 30 or 60 Hz a 300 km/h brake point is pinned to within about 6 m; at 10 or 20 Hz, about 8 m.
So choose 30 Hz or 60 Hz. For StintLab's 5 m grid the two are practically the same, and the traffic goes from the game to StintLab on your own PC without touching your network.
F1 25 or 2026 Season Pack format?
F1 25 can send its telemetry in two layouts, and StintLab reads both. The 2026 Season Pack layout is mostly the 2025 one, but every per-car list holds 24 cars instead of 22, and four of the per-car entries StintLab reads — car telemetry, participants, motion and car status — changed size.
That second kind of change is the dangerous kind. Read a 2026 packet with the 2025 layout and nothing crashes: the bytes are all there, they are simply the wrong ones, and out come numbers that look plausible and are not yours — a trace built from another car's bytes, a lap filed under the wrong team. So StintLab measures every Lap Data, Participants and Car Telemetry packet against the size its 2026 layout predicts. One mismatch and it stops reading that format for the rest of the run, turns the tray badge amber and tells you to switch to F1 25 — rather than filing a season of quietly wrong laps.
The full list of what changed, packet by packet, is in F1 25 telemetry, explained.
Check that it is working
Drive one full lap and cross the line. The lap is written to disk the moment the game reports its time, so View → My laps shows it straight away — your session listed by date and circuit, the lap inside it with its sectors.
If you see nothing, do not start changing things at random. Open Help → Setup check. It lists four things — StintLab itself, your laps folder, F1 and Assetto Corsa — each marked Working, Needs attention or Not seen yet, with what StintLab can actually see right now and the exact change that fixes it. It is built from live state, so you can change a setting in the game, reopen it, and watch the check turn green.
“Not seen yet” is not an error: a game StintLab has never heard from may simply not be running. It becomes a problem only when the game is running, you are on track, and it still says so.
Troubleshooting: when no laps appear
Almost every setup problem is one of these. Setup check names each of them in its own words.
| What you see | Why | What to do |
|---|---|---|
| F1 “Not seen yet” while you are on track | The game is not sending to StintLab: telemetry off, or a different IP address or port. | UDP Telemetry On, IP 127.0.0.1, port 20777, Broadcast Off. Drive a lap. |
| “Needs attention” about the port — or silence | Another program already has port 20777, usually another telemetry tool. If both manage to open it, there may be no warning at all: one of them simply stops hearing the game. | Close it and restart StintLab, or set [f1] port in settings.toml and the same port in the game. |
| “Packets are arriving in format …, which this build of StintLab does not recognise” | UDP Format is set to a layout StintLab does not read, such as an older year’s. | Set UDP Format to F1 25 (or the 2026 Season Pack) and drive a lap. |
| “…its packets are not the size StintLab expects”, amber badge | The 2026 layout check failed — most likely a game update moved something. | Switch UDP Format to F1 25; laps record normally. Details are in stintlab.log. |
| A lap listed as “no telemetry” | The game timed the lap but no car telemetry arrived during it. | If it happens on every lap, recheck the settings above and read stintlab.log (Help → Open log). |
| Windows Firewall asks about StintLab | StintLab opens a local UDP listener on first run. | Allowing it on private networks is enough — the game sends from the same PC. |
| Red badge | StintLab cannot write to its own folder. | Setup check shows the path. Point STINTLAB_HOME at a folder you can write to and restart. |
Two more things worth knowing. Assetto Corsa keeps recording whatever happens to the F1 port — it is read a different way, with nothing to switch on (see Assetto Corsa telemetry). And if StintLab cannot recognise a packet at all, it drops it with a line in the log rather than crashing; one bad packet never costs you the evening.
What to do with your first laps
Telemetry is only useful once it answers a question. With a few laps recorded:
- Compare two laps — tick your best and a slower one, and find where the gap opens.
- Find your theoretical best — the lap you have already driven, just not in one go.
- Follow a method — baseline, three sections, drill, re-measure.
- Learn what the game sends — the packets, what each is for, and what StintLab records per lap.
Questions
What are the correct F1 25 telemetry settings for StintLab?
UDP Telemetry On, UDP Broadcast Mode Off, UDP IP Address 127.0.0.1, UDP Port 20777, UDP Format F1 25 or F1 25: 2026 Season Pack. A send rate of 30 Hz or 60 Hz gives the finest traces, but any rate records every lap.
Which UDP format should I pick if I play the 2026 Season Pack?
Either works. StintLab reads the 2026 Season Pack format natively and checks every Lap Data, Participants and Car Telemetry packet against the size its layout predicts; if the check ever fails it stops reading that format and tells you to switch to F1 25. That layout has not yet been confirmed against a live 2026 session on a racing PC, so if you want the most proven option, choose F1 25.
Does the send rate change my lap times?
No. Lap and sector times come from the game's own timing, to the millisecond, whatever the send rate. The send rate only decides how often the game reports speed, pedals and position, which sets how finely the lap trace is drawn.
Can I run StintLab and another telemetry tool at the same time?
Not reliably on the same port. The game sends to one address and port, and when two programs both listen on it, only one of them gets each packet — and Windows may not report the clash at all. Either close the other tool, or give StintLab another port in settings.toml and set the same port in the game — in which case the other tool stops hearing the game, unless one of the two can forward packets to the other.
Does StintLab work with F1 25 on PlayStation or Xbox?
It is not sold as supported. StintLab is a Windows app built and set up for F1 25 running on the same PC, which is why the address is 127.0.0.1. Sending telemetry from a console to a PC on your network is not a setup StintLab has been verified with, so it is not promised here.
Does it read F1 24, F1 23 or older F1 games?
No. Earlier F1 games send an older packet format with different layouts, and StintLab reads only the F1 25 and F1 25: 2026 Season Pack formats. If the game sends a format StintLab does not read, Setup check names it and says which setting to change.
Do I have to change these settings every time I play?
No. The game keeps its telemetry settings with the rest of its settings, and StintLab needs no setup of its own — it has no settings file unless you create one.
Why does a lap say ‘no telemetry’?
The game timed the lap, but no car telemetry arrived at any point while you drove it. StintLab still lists the lap with its time and sectors; it just cannot draw it. If it happens on every lap, check the settings above and open stintlab.log from Help → Open log.