Why does 1px equal 1pt in photoshop but not on the web? [duplicate]

Please explain why in Photoshop setting a font size to 16pt or 16px looks exactly the same size but if I do the same test on a web site, the font-sizes are VERY different.

Example on the web

Web example of 16px and 16pt

Why would Photoshop consider 1px = 1pt but the web show them as very different sizes? What are they doing differently?

Answer

Photoshop does not treat 1px = 1 pt. Except at a specific situation.

This is when the image is set to 72 ppi + you are using pt as a unit + you have the point/pica set to 72 pt/inch.

The explanation is that if you set the ppi to 72, it matches the idea that you can have 72 points on each inch.

You can see this in action changing this values in Photoshop (units and ppi resolution) Put for example your document at 300ppi and you will se a really big font at the same 72 pts.

On a windows environment the overall settings could be at 96 ppi which does not match that 72 criteria.

In fact on a web it is very difficult to set real phisical units, some devices are now declaring the pixel density, which gives a clue on what are the real life dimensions, but not all of them.

Attribution
Source : Link , Question Author : Justin , Answer Author : Rafael

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