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SpeedReflex

How fast are you, really?

Test Your Reaction Time. Check Your Real Speed.

Test your reflexes with frame-accurate reaction tests, or turn your phone into a GPS speedometer for the car, bike, train or plane. Free, private and instant — no app, no sign-up.

Start Reaction TestOpen Speedometer
Start Reaction TestF1 startOpen Speedometer

Reflex

Reaction Time Tests

Measure how quickly you respond to what you see and hear — from a single flash or beep to a full Formula 1 start sequence.

Reaction Time Test

Five frame-accurate attempts, your average, best, consistency and percentile.

Open Test

F1 Reaction Time Test

Five red lights, a random hold, lights out. See where you would launch on a 20-car grid.

Open Test

Audio Reaction Time Test

React to a beep instead of a flash — and see how your ears compare with your eyes.

Open Test

Average Reaction Time

What’s normal, good and fast — by age, stimulus and device, with sources.

Read Guide

GPS

Speed Tests for Every Journey

One precise GPS speedometer, tuned for how you travel: the right units, gauge range and features for each.

Online Speedometer

How fast am I going? Live GPS speed, max, average and distance for any trip.

Open Test

Car Speed Test

Check your true speed against the dashboard, with HUD mirror mode and speed alerts.

Open Test

Bike Speed Test

Speed, distance and moving average for bicycles, e-bikes and motorbikes.

Open Test

Bus Speed Test

Check how fast your bus or coach is going from your seat, with GPS accuracy shown.

Open Test

Train Speed Test

See how fast your train is really going — from commuter lines to 300 km/h high-speed rail.

Open Test

Flight Speed Test

Ground speed, altitude and heading at 35,000 ft — works in airplane mode.

Open Test

Speed × reflexes

Where Speed Meets Reaction Time

On the road, the two numbers SpeedReflex measures multiply. Every tenth of a second you take to react is distance travelled before you even brake.

Stopping Distance Calculator

Thinking plus braking distance at any speed, reaction time and road condition.

Open Calculator

23 m

Typical stopping distance at 30 mph

96 m

Typical stopping distance at 70 mph

3.1 m

Travelled per 0.1 s of reaction at 70 mph

Why SpeedReflex

Built to Be Accurate, Not Just Fast

Frame-Accurate Timing

Reaction tests start the clock on the frame the signal is painted and read the hardware timestamp of your press.

Colour-Blind-Safe Signal

A dark-to-blue flash is a big brightness change, so it reads just as clearly with red–green colour blindness.

Private by Design

No accounts, no tracking. GPS positions and test history never leave your device.

HUD & Always-On Screen

Mirror your speed onto the windshield at night. The screen stays awake while a trip runs.

Speed Alerts

Set a limit for your car, e-bike or scooter and get a beep and vibration the moment you cross it.

Progress & GPX Export

Track your reaction times over weeks, and export any trip as GPX for Strava, Komoot or Google Earth.

The tests are built for everyday curiosity, practice and trips — not as medical, laboratory or calibrated instruments. Your screen, input device and GPS signal all affect the result, so each tool says what it measures and what can skew it. The details are on how SpeedReflex measures reaction time and speed.

Benchmarks

Numbers Worth Knowing

Median browser reaction time in our population model
250 ms
Start reaction commonly reported for Formula 1 drivers
≈0.2 s
Where EU e-bike pedal assistance cuts out
25 km/h
Typical ground speed of a jet at cruise, before wind
900 km/h

SpeedReflex

Transparency, Trust & Support

SpeedReflex is built on frame-accurate science, zero tracking, and open web standards. Learn how our measurements work, review our driving and medical disclaimers, or get in touch with our team.

About Us

How we measure speed and reaction times: frame-synced paint timing, Doppler GPS filtering, and honest population models.

Read our methods

Contact Us

Have a question, device timing issue, or feature request? Send our technical team a message or email us directly.

Get in touch

Privacy Policy

100% on-device processing. No accounts, no user telemetry, no tracking cookies, and zero coordinate transmission.

Review privacy policy

Terms & Conditions

Recreational usage guidelines, essential driving and passenger safety disclaimers, and health notices.

Read terms of use

FAQ

Frequently Asked Questions

Is SpeedReflex free to use?

Yes. Every reaction time test, F1 starting simulator, and GPS speedometer on SpeedReflex is 100% free with unlimited trials and no account or subscription required.

Do I need to install an app from an app store?

No app download is needed. SpeedReflex operates directly within your mobile or desktop web browser (Safari, Chrome, Firefox, Edge). You can easily tap "Add to Home Screen" on iOS or Android for instantaneous, full-screen progressive web access.

How accurate are browser-based reaction time tests?

SpeedReflex is engineered for frame-accurate precision. Unlike standard web tests that start timers before frames are rendered, our tests synchronize clock start with the browser's display paint using requestAnimationFrame and read raw hardware event timestamps (event.timeStamp). This eliminates up to 17 ms of browser paint lag.

How accurate is an online GPS speedometer compared to a vehicle dashboard?

Satellite GPS calculates your true velocity over the ground via radio Doppler frequency shift, accurate to within 1–2 km/h under open sky. By contrast, factory car speedometers are legally calibrated (UN ECE Reg 39) to read 3% to 8% higher than actual road speed to prevent accidental speeding.

Which devices support the GPS speedometers?

Any smartphone or cellular tablet equipped with an internal GPS receiver (including iPhone, iPad with cellular, and Android devices). Standard laptops and desktops do not have GPS chips and cannot provide continuous moving velocity.

Is my location data or reaction score private?

Completely private. All GPS geolocation coordinates and reaction time metrics are computed locally on your device hardware. Zero location data or personal metrics are ever sent to our servers.

Which test should I start with?

Depending on your goal: Begin with the Reaction Time Test for a baseline, then challenge yourself on the F1 Reaction Time Test. For velocity, open the Online Speedometer or select vehicle-specific modes. For road safety, calculate stopping distances with the Stopping Distance Calculator.

Can I export my speed track or reaction history?

Yes. After running a speed test, tap Export GPX to download a standard GPS track file ready for Strava, Komoot, or Google Earth. Your reflex scores can also be copied and shared as a challenge link with friends.

Ready When You Are.

Five attempts, about thirty seconds. See where your reflexes really stand.

Start Reaction TestTry the F1 Start