Best answer: In order to attain the maximum charging speed of 21W on your Pixel 6 (23W on Pixel 6 Pro), the charger must support Power Delivery (PD, Programmable Power Supply (PPS), and be rated to 24W or higher. You also need an e-marked cable that can negotiate the exact current between the charger and the phone.
What you need to reach maximum Pixel 6 charging speeds on a wired charger
The best Pixel 6 chargers need Programmable Power Supply, which is a specialized certification within the larger Power Delivery spec used to fast-charge everything from your earbuds to your Macbook and beyond. PPS chargers were quite difficult to find when the Samsung Galaxy Note 10+ started using them for its short-lived 45W fast charging frenzy, but since Samsung uses it for its 25W Super Fast Charging as well, it's gotten much, much easier to find.
Of course, since PPS chargers were originally designed for laptops — to help limit heat buildup and preserve the multi-hundred-dollar battery inside your trusty workhorse — most PPS chargers are 45W and up. Even though the Pixel 6 Pro may only charge at a maximum of 21W, there's little point in getting a 30W charger these days as practically all tablets and laptops use USB-C Power Delivery to charge. Grab a 45-90W charger that you can use for your Macbook, Nintendo Switch, and any other USB-C equipped device in your home. Futureproof your purpose since today's best chargers can last you a decade or more.
One more requirement for top-speed wired Pixel 6 charging often overlooked is the cable. Not all USB-C cables are created equal; some prioritize data speed over charging speed, some are USB 2.0 and some are USB 3.2 Gen 2 x 2 (hey, I didn't name it, but I'd like to slap whoever did), and some are e-marked while most older cables are not. PPS charging and thus Pixel 6 fast charging requires an e-marked cable so that the charger and your Pixel 6 can talk to each other and negotiate exactly what voltage/amperage it needs at the time.
Many PPS chargers come with e-marked cables in-box specifically to avoid uninformed buyers complaining/returning the product because they don't realize PPS needs an e-marked cable. You have now been informed so that you can make a better buying decision and avoid cable frustrations down the line.
Why it doesn't matter: You'll barely ever see top speed anyway
The most important limitation to 23W wired charging isn't on the charger or the cable, it's on the phone and on Google. Full 23W fast charging is only possible when your phone is under 50%, and even then, you still might not see it unless you're starting from close to empty. Google designed its charging protocols on the Pixel 6 series "to strike a balance between battery life, longevity and fast charging," as it said when they had to explain Pixel 6 charging speeds on its own forum.
If you're below 50%, Google enables the higher charging speeds to ensure you get to half-full quickly, but once you hit 50%, speeds will slow down until you eventually reach full an hour later. Google does this to better manage heat and extend the life of your battery, which is great except for when I'd really like to charge from 60% back up to 85% before I head out for a long evening of fireworks and maybe a tryst with a prince at the Magic Kingdom. If you're above 50%, you'll only see charging speeds between 9-15W, so remember that the first 50% takes half an hour and the second 50% takes a whole hour.
What you need to reach maximum Pixel 6 charging speeds on a wireless charger
Things are blessedly much easier to spell out when it comes to fast wireless charging on the Pixel 6. You can only achieve the 23W top charging speed with the Google Pixel Stand (2nd Gen), but it's $80 and just like wired charging, you can expect speeds to slow the closer you get to full. I'm very much looking forward to reviewing the Pixel Stand to see just how quiet its fan is and how far the features on the Pixel 6 have come, but there's admittedly little reason to spend so much money unless you need the latest everything.
In order to get the 15W wireless charging speeds that the Pixel 5 enjoyed — and which you'll get far more adaptability and choice on — you need to look for a wireless charging pad or stand that supports Extended Power Profile (EPP) at 15W output. Most of the best wireless chargers support EPP, and if you see another charger that catches your fancy but doesn't list EPP or the Pixel 6 among its supported 15W phones, you can head to the Wireless Power Consortium's Product Database and search for the product by brand name. Product listings here will tell you the maximum output speed, whether or not it supports EPP, and if it has Samsung's proprietary charging tech in it (which most do because Samsung is popular).
If you need suggestions for Pixel-perfect wireless charging options from our best wireless chargers, the iOttie iON Wireless Duo is a great stand and the Anker PowerWave Alloy is a compact, sleek pad. Whether wired or wireless, grab something long-lasting and widely compatible, because these chargers may very well outlive both your Pixel 6 and the phone you get after it.
Anker Nano II 45W Fast Charger
This 45W charger is great for charging Chromebooks, Macbooks, and yes, the Pixel 6 and 6 Pro, too! While it doesn't come with an e-marked cable, your shiny new phone did, and this super-shrunk charger fits perfectly in a pocket, purse, or backpack.
$40 at Amazon
Spigen (GaN Fast) 45W Super Fast Charger
Spigen is gracious enough to include a proper cable in the box in order for you to achieve top speeds. While primarily marketed towards the Samsung Galaxy line, both use PPS, so Spigen's charger works just as well for the Pixel 6 and 6 Pro.
$30 at Amazon