Slack pasted the HTML source because rich text hit a plain field

You laid out a signature in the snippet editor: a bold name, a blue link, a line of smaller gray type under it.

In mail it looks designed. The same abbreviation in Slack shows <p> and <a href>, or a bare URL with the color gone. The expander did not break. You fed rich text to a field that strips HTML.

A snippet file has an environment. plain is characters. rich is HTML: headings, lists, tables, images, links that carry style. Both exist on the free tier. See Snippets. A pretty editor is not a promise the destination will honor the markup.

Ask where it lands, then pick the environment

When a rich file expands, the clipboard carries HTML plus a plain fallback. The target app chooses. Mail, documents, and note apps that accept HTML keep bold and link color. The terminal, some chat composers, and any field that only takes characters will strip the style. If the strip is sloppy, the tags land as text — that is the Slack screenshot you already hate.

A styled link is only a styled link in a surface that keeps HTML. The other person sees a clickable “docs” label, or a raw https://…, because of their field, not because the preview in the main window looked finished.

One snippet can hold two files: rich for mail, plain for chat and the terminal, each with its own abbreviation. Do not keep two drifting “signature” snippets. How extra files hang off one row is in Snippets.

1. Open the snippet you type in chat and check the file environment.
2. Keep rich for mail and documents. Point chat at plain, or add a second plain file.
3. Expand the chat abbreviation in Slack. You should see words, not tags.

The clipboard window can paste without formatting after the fact. That is a second strip, for retrieval. It does not replace choosing the right environment. See Clipboard.

FillIn decides what you type this time. It does not change whether the destination will keep HTML. After the form submits, the insert still follows that file’s environment. Do not paste a blob of tags into a fill-in field and hope the chat composer will restyle it.

Style is for apps that keep it

Lists, tables, and images hold only when the destination treats the paste as rich. If the box only accepts characters, the layout collapses. Do not mark support replies, crash templates, or shell commands rich because the home editor looked nicer.

Script environments are a different contract: the insert is stdout, not layout. Boilerplate belongs in plain text or a script. That article is Developer boilerplate. Adaptive case changes letter case on the typed abbreviation; a rich file still follows its own environment. See Expand.

Do not

• Do not paste HTML source into a plain file and hope chat will restyle it.
• Do not send one rich snippet into every app. Stripping is the destination’s behavior, not a toggle you turn off in Settings.
• Do not disable “require a trigger key” to fix formatting. A misfire and a tag dump are different accidents.

Related: Snippets, FillIn.