It’s an HTML. Since the abbreviation HTML is pronounced as individual letters, and the "H" starts with a vowel sound ("eich"), we use the indefinite article "an".

It’s an HTML. Since the abbreviation HTML is pronounced as individual letters, and the "H" starts with a vowel sound ("eich"), we use the indefinite article "an".

An HTML document contains texts and some tags written between the symbols "<" and ">".

A HTML document contains texts and some tags written between the symbols "<" and ">".

Remember, the rule for using "a" or "an" is based on pronunciation, not spelling; thus, when speaking about the "HyperText Markup Language", we say "an HTML document", "an HTML file", "an HTML page", "an HTML element", "an HTML table", etc.

The protocol requires an HTML file.

Do you know how to create an HTML table?

Follow the same convention to say an H, an HDL test, an HDMI cable, an HIV test (Human Immunodeficiency Virus), an HPV (Human Papilloma Virus), or an HTTP connection.

An HTTP connection requires a TCP session between two computing devices.