The SMS protocol does not carry any formatting information. An SMS is plain text, encoded in simple characters, without style metadata. On a Samsung Galaxy, the visible underlining on the screen during typing comes from autocorrect, not from formatting transmitted to the recipient.
The word underlined in red indicates a mistake detected by the Samsung keyboard, and the word highlighted in gray indicates a correction by predictive text. None of these effects appear in the message received by your correspondent.
Why the Samsung keyboard displays misleading underlining
The confusion arises from the visual behavior of the Samsung keyboard (Samsung Keyboard). When spell check is enabled, each misspelled word receives a red underline. When predictive text automatically corrects a term, that term appears highlighted in gray.
Both indicators disappear as soon as the message is sent. Your correspondent receives uniformly black text on a white background, with no trace of underlining or highlighting. The Samsung underlining is a proofreading tool, not a formatting tool.
To verify, disable predictive text in the Samsung keyboard settings (Settings > General management > Samsung keyboard settings > Predictive text). The gray highlighting disappears, and only the red underline from spell check remains. This confirms that these are two distinct mechanisms, both limited to your screen.
If you are looking to underline a word in a Samsung SMS so that your recipient actually sees it formatted, you need to step outside the traditional SMS channel and use a messaging app that supports formatting.
Text formatting on WhatsApp and Telegram from a Samsung
WhatsApp and Telegram use their own messaging protocol, which supports formatting. On these apps, installed on most Samsungs, formatting works through special characters surrounding the text.
WhatsApp formatting shortcuts
WhatsApp does not offer an “underline” button in its interface. Underlining is not natively supported. The three available formatting options are bold, italic, and strikethrough.
- To make a word bold, surround it with asterisks: *word* becomes word
- For italic, use underscores: _word_ displays the word in italic
- For strikethrough text, surround it with tildes: ~word~ displays the word with a horizontal line
On WhatsApp, there is another method: select the word by pressing and holding it, then use the context menu (the three vertical dots on some Samsungs) to choose the desired formatting among bold, italic, and strikethrough.
Formatting on Telegram
Telegram goes further than WhatsApp. The app supports bold, italic, strikethrough, monospace, and underlining. To underline a word on Telegram, select it by pressing and holding, then choose the “Underline” option from the formatting menu.
Thus, Telegram is the only common messaging app that actually allows you to send underlined text to your correspondent from a Samsung.
Unicode text generators to simulate underlining via SMS
There is a technique that works even with traditional SMS. Online tools (sometimes called “text formatters”) convert normal text into special Unicode characters that visually mimic underlining, bold, or italic.
The principle: each letter is replaced by a decorative Unicode character that resembles the original letter but belongs to a different block of the Unicode standard. The result looks like underlined text, even in a plain SMS, because these are not standard Latin letters.
The process is simple. Open a Unicode formatting site in your Samsung’s browser, enter the word to be underlined, copy the result, and then paste it into your SMS. The recipient will see the “underlined” text regardless of their phone, as long as it supports the relevant Unicode characters.
Two limitations to be aware of:
- Unicode text consumes more characters per SMS. A message with a few formatted words may occupy several SMS segments instead of just one, which can incur additional costs depending on your plan
- Some older phones or certain operating systems display empty squares instead of special Unicode characters. Readability is not guaranteed on all devices
- Unicode characters are not indexed like normal text: searching through messages will not find a word formatted in this way
Samsung Messages and RCS: what formatting options
RCS (Rich Communication Services) is the successor to SMS pushed by Google and gradually adopted by carriers. On recent Samsungs, the Google Messages app activates RCS by default when both correspondents are compatible.
RCS does not support text underlining. The protocol allows sending high-resolution images, read receipts, and emoji reactions, but does not allow formatting the body of the message (neither bold, nor italic, nor underlined).
RCS thus remains at the same level as traditional SMS in terms of text formatting. The difference lies in media and interactions, not typography.
To achieve visually underlined text in a Samsung message, the only two reliable options remain using a third-party app like Telegram (which transmits actual underlining) or resorting to Unicode characters (which simulate the appearance). The choice depends on the app used by your correspondent and the display reliability you expect.