The plain ✓ U+2713 CHECK MARK is the safest tick for text: it has the HTML entity ✓ and never turns into an emoji. ✔ U+2714 HEAVY CHECK MARK is bolder but is also an emoji, so some platforms may draw it in colour. ✅ U+2705 is always a colour emoji.
For a to-do list, pair an empty ballot box ☐ with ☑ (checked) and ☒ (crossed). For a “no”, ✗ and ✘ match the style of ✓ and ✔; ❌ is the emoji equivalent. The square root sign √ is sometimes used as a tick in old documents, but screen readers announce it as “square root”, so avoid it.
Click any symbol to copy it. Names link to the full character page with every encoding.