# Tesla HW3 vs HW4: What's the Difference When Buying a Used Tesla?

> HW3 vs HW4 explained for used Tesla buyers: cameras, computer, FSD (Supervised) support, which model years have which, how to check any car's screen, and…

Canonical: https://www.premiumautosinc.com/tesla-hw3-vs-hw4-differences  
Last updated: 2026-11-08

By Premium Autos · Published 2026-11-08 · 4 min read

## What are HW3 and HW4?

"HW" stands for hardware. Every Tesla built since 2016 has a computer behind the glovebox that reads the car's cameras and runs Autopilot and Full Self-Driving. Tesla has made several versions of it: HW3 (Hardware 3, also called AI3) and HW4 (Hardware 4, also called AI4) are the two you will find in most used Teslas today. Think of it like the processor in a phone: the car looks the same from the outside, but the newer chip and cameras can run newer driving software.

## The short answer

HW4 (Tesla also calls it AI4) is the newer one: it has more computing power and sharper cameras, and it gets Tesla's newest Full Self-Driving (Supervised) software first. HW3 (AI3) still runs Autopilot, Enhanced Autopilot and a lighter version of FSD (Supervised) well for everyday driving. A car cannot be changed from HW3 to HW4 at a dealer or a Tesla service center today, so the computer a used Tesla left the factory with is the one it has. If you plan to use FSD a lot, shop for HW4. If you mainly want the car, the range and standard Autopilot, an HW3 Tesla usually costs less and does that job well.

Every Tesla on our site shows an **HW3** or **HW4** badge when we know which computer it has. Shop [used Teslas with HW4](https://www.premiumautosinc.com/used-cars-in-norco-el-monte-ca?make=tesla&features=hw4) or [used Teslas with HW3](https://www.premiumautosinc.com/used-cars-in-norco-el-monte-ca?make=tesla&features=hw3).

## HW3 vs HW4 side by side

|  | HW3 (AI3) | HW4 (AI4) |
| --- | --- | --- |
| First used | 2019 | 2023 (Model S/X and some Model Y), Model 3 from 2024 |
| Cameras | About 1.2 megapixels | About 5 megapixels, sharper at distance and at night |
| Computer | Tesla's first in-house self-driving chip | Newer, more powerful chip with more memory |
| Autopilot (lane keeping, traffic-aware cruise) | Yes | Yes |
| FSD (Supervised) | Yes, a lighter build that arrives after HW4's | Yes, Tesla's newest builds first |
| Unsupervised FSD / Robotaxi | Tesla has said HW3 will not do this without new hardware | Tesla's current platform for it |
| Typical used price | Lower (older model years) | Higher (newer model years) |

Megapixel figures are widely reported numbers for the camera sensors, not a Tesla spec sheet. Both computers are driver assistance: the driver must watch the road and be ready to take over at all times.

## What the difference means on the road

- **Everyday Autopilot feels about the same.** Lane keeping and traffic-aware cruise control work on both computers. Most buyers who never pay for FSD will not notice a difference on the freeway.
- **FSD (Supervised) is where HW4 pulls ahead.** Tesla trains its newest FSD builds for HW4 first. HW3 cars now run a lighter "Lite" version of the same FSD generation, which owners report drives smoothly, but it arrives later and has less headroom for future features.
- **Sharper cameras help Sentry Mode and Dashcam clips too.** HW4 cars record clearer video, which is handy if you ever need a clip for insurance.
- **The long-term question is unsupervised driving.** Tesla has said HW3 cars will not run unsupervised FSD and has talked about a hardware upgrade for HW3 owners who bought FSD outright. No date or price has been confirmed for buyers of used cars, so we do not count on it when we price a car. Check Tesla's own support pages for the latest.

## Which model years have which computer

The VIN does not say which computer a Tesla has, and dealer feeds usually leave it out. Tesla switched computers partway through some model years, so the year alone does not always answer it. This is the rule our listings use:

| Model | HW3 (every car) | Built with either (ask us) | HW4 (every car) |
| --- | --- | --- | --- |
| Model 3 | 2020 to 2023 | 2019 | 2024 built in Fremont or Austin, 2025 and newer |
| Model Y | 2020 to 2022 | 2023 | 2024 built in Fremont or Austin, 2025 and newer |
| Model S and Model X | 2020 to 2022 | 2019 and 2023 | 2024 and newer |
| Cybertruck |  |  | All |

Cars from 2018 and older left the factory with older computers (HW2 or HW2.5), and some were later upgraded to HW3, so we only label those after checking the car. For a "built with either" year, our staff check the car itself before we show a badge.

## How to check any Tesla yourself

On the car's touchscreen, tap **Controls**, then **Software**, then **Additional Vehicle Information**. The line "Autopilot Computer" shows "Full self-driving computer" for HW3 or "AI4" / "Hardware 4" for HW4 (the exact wording depends on the software version). It takes ten seconds, and you can ask us to send a photo of that screen for any Tesla in our inventory.

## Is FSD included with the car?

The computer and the FSD software are two different things. A Tesla can have HW4 and no FSD, or HW3 with FSD that a previous owner bought. FSD that was bought outright normally stays with the car; a trial or monthly subscription does not. Our car pages say when FSD has been confirmed as bought. When it is not included, you can add it anytime with Tesla's FSD (Supervised) subscription, $99/month (Tesla sets the price and can change it).

## Which should you buy?

- **Pick HW4 if** you want to use FSD (Supervised) often, want Tesla's newest software first, or plan to keep the car for many years. Start with [Model Y with HW4](https://www.premiumautosinc.com/used-cars-in-norco-el-monte-ca?make=tesla&model=model-y&features=hw4) or [Model 3 with HW4](https://www.premiumautosinc.com/used-cars-in-norco-el-monte-ca?make=tesla&model=model-3&features=hw4).
- **Pick HW3 if** you want the lowest price on a Tesla, mostly use regular Autopilot, and care more about range, condition and battery health than self-driving. See [Model 3 with HW3](https://www.premiumautosinc.com/used-cars-in-norco-el-monte-ca?make=tesla&model=model-3&features=hw3) or [Model Y with HW3](https://www.premiumautosinc.com/used-cars-in-norco-el-monte-ca?make=tesla&model=model-y&features=hw3).
- **Either way,** check battery health, tires and the vehicle history before the computer. Our [battery health page](https://www.premiumautosinc.com/battery-health) explains the estimates on our listings, and every Tesla we sell is listed by VIN online first.

## See it in person

Premium Autos has Teslas at both stores, Norco and South El Monte, and our team can pull up the Autopilot computer screen on any car while you are there. Browse [all used Teslas](https://www.premiumautosinc.com/used-cars-in-norco-el-monte-ca?make=tesla), or [contact us](https://www.premiumautosinc.com/contact) and ask about a specific car.

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