# What is Identity-H encoding, should it be avoided and if so, how?

When I create a document with multiple fonts (using xelatex and xeCJK), subsets of all these fonts are included in the document. The document’s properties shown in evince, in the Fonts tab, show the following:

1. Most of the fonts are shown as name-style-Identity-H, e.g. LibertinusSans-Bold-Identity-H (but some don’t end on Identity-H).
2. All of them further show either Type 1C (CID) or TrueType (CID).
3. Below all of them there’s a line saying: Encoding: Identity-H.

(When I check the Fonts tab in a pdftex-created document I got from someone else, the fonts are all Type 1 and Encoding: Custom. Other documents have other encodings or also Identity-H)

To extract text when this encoding is used, the PDF also needs a “ToUnicode CMap”. You cannot see if one of these is present.

What does Identity-H really mean and how does xelatex behave concerning this?