Email Signature Character Limit

Email signature character limits vary by email client and context. Gmail's web signature editor caps signatures at 10,000 characters of HTML, which is ample for any well-designed signature but a hard ceiling if the HTML is bloated. Outlook desktop does not have a single character limit but practical limits emerge: signatures over a few KB cause noticeable compose-time delays, and signatures using significant inline imagery can trigger spam filters that flag large messages. The more important limit is file weight: signatures should ideally render at under 100KB total including all embedded images, because larger signatures slow loading on mobile, increase email storage costs, and can affect deliverability when sent at high volume. Sophisticated platforms optimize HTML output to be compact (no inline CSS bloat, optimized image references, no unnecessary whitespace) so the rendered signature stays well under any client limit while remaining visually rich. Plain-text fallbacks should be similarly concise.