Since the June 2019 update patch, Android phones running Android 8 (Oreo) and above can scan QR Codes using the phone's camera app. Apple phones have this camera functionality as well.
To scan a QR code, open the camera app, hold it towards the QR code for a few seconds for the camera to register the QR code. You may see a small banner, yellowed QR code (like mine, via the Moto G7), or similar graphic. Touch the QR code to open the link. From my Android phone:
Phones running Android 7 (Nougat) require a third party QR code app (see below).
Creating a QR code is relatively easy, but there are a couple of things to keep in mind to make the best image possible:
Make the code easy to scan: the bigger the code, the easier it is for the scanner in your phone to "read" the image. Anything smaller than 1" x 1" is not recommended.
Leave some white space around the code, at least 1/8" for the scanner application to visually cue into the code.
Keep links or linked information short--use a link shortener like Bit.ly. The shorter the link or message you embed in the code the better the resolution and link length, and the less crowded the code will look. Be warned: QR codes created in either service are considered public data, so your stats/clicks are available for anyone to see.
Avoid QR code generators that re-direct the scanned link to their own product pages. The code generators below do not redirect links.
QR codes enable content to be accessed via a mobile device, so make the end destination a mobile-friendly page.
Goo.gl ended support for QR code creation in March 2018, unless you created them in the past.
Create various codes (datamatrix, Aztec, micro) with an extensive list of actions (SMS, links, free text, maps); URL shortening options (Bit.ly, Goo.gl, Is.gd, etc.); download options (PDF, SVG, etc.); color options; large codes; no analytics.
If you have Google Assistant on your phone then you have Google Lens on your phone. Google Lens lets you scan images, text, photos, and even QR codes.
To scan, simply open Google Assistant and click on the camera icon on the lower, right side of the assistant. Your phone's camera will activate and you can scan the QR code in question. You can also download Google Lens at https://lens.google.com/