WhatsApp text formatting

Contract

Enforces WhatsApp's native text markup on every message you send into a WhatsApp chat: single-character emphasis delimiters, bare auto-linked URLs, and no heading syntax. Apply whenever the reply is destined for WhatsApp (a 1:1 chat or a group). The base model's default is standard Markdown, which WhatsApp does NOT render — doubled delimiters and [text](url) links arrive as literal characters.

Rules

WhatsApp emphasis uses ONE delimiter character on each side, not two. This is the whole point: the form is deliberately different from Markdown.

1. Bold — wrap the text in a SINGLE asterisk: *text*. Never **text**. A doubled

asterisk is NOT bold on WhatsApp; it renders as a literal * plus italic plus a literal *.

1. Italic — wrap the text in a SINGLE underscore: _text_. Never *text* for italic

(that is bold here) and never __text__ (doubled underscores render literally).

1. Strikethrough — wrap the text in a SINGLE tilde: ~text~. Never ~~text~~; the

doubled-tilde Markdown form renders as literal tildes around the words.

1. Inline monospace — wrap in single backticks: text . Use it for short code,

identifiers, commands, or values that must not be auto-formatted.

1. Monospace block — wrap a multi-line snippet in triple backticks on their own lines.

Use it for code, logs, or anything where line breaks and spacing must be preserved.

1. Links — paste the BARE URL. Write https://example.com on its own and WhatsApp

auto-links it. NEVER use Markdown link syntax [label](https://example.com) — WhatsApp does not parse it, so the recipient sees the literal characters [label](https://example.com) and gets no clickable link. If you want a label, put the words and the bare URL near each other.

1. No headings. WhatsApp has no #/## heading syntax. A line that starts with # Title

shows the literal #. To make a heading-like line, BOLD it instead: a bold title line.

1. Delimiter placement. The delimiter must hug the text with no inner spaces — the run must

start and end against a non-space character. Put whitespace (or the message start/end) on the OUTSIDE of the delimiters so WhatsApp recognizes the span.

1. Combining styles — nest single delimiters: bold + italic is one asterisk pair wrapping

one underscore pair. Keep every delimiter balanced (one opener, one closer).

1. Lists & quotes (optional). A line beginning - (or * ) becomes a bullet; 1.

becomes a numbered item; > becomes a quote. These match Markdown and are safe to use; the emphasis markup inside them still follows rules 1-3.

Worked examples

One BEFORE (the Markdown the base defaults to) → AFTER (the WhatsApp-native form).

Bold — server notice. Tell the channel maintenance is over, "resolved" emphasized.

BEFORE:  Maintenance is **resolved** — all systems are back online.
AFTER:   Maintenance is *resolved* — all systems are back online.

Double asterisk → single asterisk.

Italic — a soft caveat.

BEFORE:  We'll aim for Friday, *though that may slip*.
AFTER:   We'll aim for Friday, _though that may slip_.

Markdown italic-by-asterisk → WhatsApp italic-by-underscore (asterisks would render bold).

Strikethrough — a corrected figure.

BEFORE:  The fee is ~~$40~~ now $25.
AFTER:   The fee is ~$40~ now $25.

Double tilde → single tilde.

Link — share a page.

BEFORE:  Sign up here: [the registration page](https://acme.example/signup)
AFTER:   Sign up here: https://acme.example/signup

Markdown link (renders as literal text on WhatsApp) → bare auto-linked URL.

Heading — a titled announcement.

BEFORE:  # Release 2.0 is live
         New dashboard and faster sync.
AFTER:   *Release 2.0 is live*
         New dashboard and faster sync.

# heading (shows a literal #) → a bold title line.

Combined — bold name + italic note.

BEFORE:  **Priya** will lead the call *(bring your notes)*.
AFTER:   *Priya* will lead the call _(bring your notes)_.

Each style switched to its single-character WhatsApp delimiter.

Monospace block — a snippet.

`
BEFORE:  Run `npm run deploy` then check the log.   (inline is fine)
AFTER:   Run `npm run deploy` then check the log.

Inline single backticks are the same on both; reserve triple backticks for multi-line blocks.

Edge cases & exceptions

• Asterisk that is NOT emphasis (a math 2 * 3, a literal bullet glyph in prose): leave a

space on at least one inner side so WhatsApp does not treat it as a delimiter, e.g. 2 * 3.

• Underscores inside a URL or identifier (my_file.py, a query string) are not italic —

WhatsApp only treats _x_ as italic when the underscores bound a word run with outer whitespace; inside a token they stay literal. Don't try to "fix" them.

• A delimiter with an inner space (* text *) does NOT render — WhatsApp ignores it and

shows the literal asterisks. Always hug the text: *text*.

• Want a literal *, _, or ~ with no formatting: separate it from word characters with a

space, or rephrase; WhatsApp has no backslash escape.

• Long code / config: use the triple-backtick block, not inline backticks, so wrapping and

indentation survive.

• A label you really want on a link: WhatsApp can't hide a URL behind link text — put the

human words and then the bare URL; never the [label](url) form.

• Mixed Markdown habits: **bold** _italic_ is half-wrong — the bold half won't render.

Convert every emphasis run, not just some.

Do / Don't

• DON'T write **bold**. ALWAYS write *bold* (single asterisk).
• DON'T write ~~strike~~. ALWAYS write ~strike~ (single tilde).
• DON'T use *text* for italic. ALWAYS use _text_ (asterisks are bold here).
• DON'T write [label](url). ALWAYS paste the bare URL.
• DON'T start a line with # for a heading. ALWAYS use a bold line instead.
• DON'T put spaces just inside the delimiters (* x *). ALWAYS hug the text (*x*).
• DON'T leave some emphasis in Markdown form. ALWAYS convert every run to single-delimiter form.

Common mistakes (the base model's wrong defaults)

• Emitting **bold** out of Markdown habit — the most common failure; it renders wrong.
• Using ~~strikethrough~~ (GitHub-flavored Markdown) instead of single ~.
• Reaching for [text](url) links, which WhatsApp shows as raw characters with no link.
• Opening a message with a #/## heading line that displays a literal #.
• Using *emphasis* meaning italic — on WhatsApp that is bold, so the intent flips.
• Padding delimiters with inner spaces so nothing renders at all.

Quick checklist

• ] Bold is a SINGLE asterisk *x*, never **x**.
• ] Italic is a SINGLE underscore _x_, never *x* or __x__.
• ] Strikethrough is a SINGLE tilde ~x~, never ~~x~~.
• ] Links are BARE URLs, never [label](url).
• ] No #/## heading lines — a bold line stands in for a heading.
• ] Delimiters hug the text (no inner spaces); every pair is balanced.