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About this tool
Resolve a CSS font stack client by client, see which fonts actually install where, and get an email-safe fallback chain.
Email Safe Font Checker resolves a CSS font-family stack the way a mail client does — first family that resolves wins — across twelve common client and platform combinations, and reports exactly which typeface each subscriber ends up seeing. Two things decide the outcome: whether the client honours @font-face at all (Gmail, Outlook on Windows, Outlook.com, Yahoo and AOL do not) and which families ship with the reader's operating system. It also flags stacks with no generic keyword at the end, the single most common cause of an email rendering in Times New Roman.
Open Email Safe Font Checker on AltFTool — it loads instantly in your browser.
Type your CSS stack into the "font-family stack" field (placeholder Georgia, 'Times New Roman', serif) or click one of the ready-made chips below it — Neutral sans, Wide sans (small type), Classic serif, System UI, Monospace or Google font with fallback.
If you load a webfont, name it in "Family loaded via @font-face (optional)" and set the Preview text; resolution re-runs immediately across every client, with no check button to press.
Read "Subscribers who see your first choice" plus the "Ends in a generic keyword" and "Clients falling through to their own default" rows and the Client / Renders / Why table, then press Copy stack under Suggested safe stack, or Copy report for the whole thing.
Resolution is shown per client and platform, not as a single vague support percentage.
Warns when a stack has no generic keyword, so nothing silently lands on the client's default.
Suggests a replacement stack that keeps your first choice and adds wide-coverage fallbacks.
Arial, Helvetica, Georgia, Times New Roman, Verdana, Trebuchet MS and Courier New are installed on Windows, macOS and iOS. None of them ship on Android, which uses Roboto and Noto, so always finish the stack with sans-serif, serif or monospace.
Only in some clients. Apple Mail on macOS and iOS, Outlook for Mac, Samsung Email and Thunderbird render @font-face; Gmail on every platform, Outlook on Windows, Outlook.com, Yahoo Mail and AOL strip it. Plan the layout around the fallback family, not the webfont.
The stack ran out of options. If none of the named families are installed and the stack does not end in a generic keyword, the client applies its own default, which is frequently a serif. Adding sans-serif to the end of the list fixes it.
Outlook 2016 through 365 on Windows renders with the Word engine, so it ignores @font-face and can drop unfamiliar families. Use an installed family, add an mso-font-alt style hint, and wrap Outlook-only overrides in a conditional comment.