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Source Serif 4

Source Serif 4 is a serif font in 8 weights with italics, also available as a variable font. Its lowercase letters are 6% wider than the typical serif font. Last updated 11 September 2025.

Source Serif 4: The quick brown fox jumps over the lazy dog 0123456789
Source Serif 4 Regular
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Editing a PDF that uses Source Serif 4

Most PDFs embed only the letters they already use. Type a new letter and many editors either refuse or swap in a different font. MythosPDF recognises Source Serif 4 from the widths stored in your PDF, loads the complete open font, and sets your new text in Source Serif 4 itself. The rest of the page is carried over untouched.

Measured metrics

Average lowercase letter width550.7 units per 1000 em
Average capital letter width680.8 units per 1000 em
Word space237 units per 1000 em
Digitstabular (every digit is 529 units wide, so columns of numbers line up)
Spacingproportional
Width of i compared with m35%
Printable ASCII characters covered94 of 94
CategorySerif

Weights and styles

Languages beyond basic Latin

Open fonts closest to Source Serif 4

Measured on every printable character both fonts contain. A smaller difference means the same words take the same space, so lines break in the same places.

  1. Noto Serif HK Regularsimilar widths (16.3 units)
  2. Noto Serif JP Regularsimilar widths (16.3 units)
  3. Noto Serif SC Regularsimilar widths (16.3 units)
  4. Noto Serif TC Regularsimilar widths (16.3 units)
  5. Noto Serif KR Regularsimilar widths (16.3 units)
  6. Bpmf Zihi Kai Std Regularsimilar widths (19.7 units)
  7. Source Serif Pro Regularsimilar widths (21.1 units)
  8. Averia Serif Libre Regularsimilar widths (25.1 units)

Compare Source Serif 4

Questions people ask

+Can I edit a PDF that uses Source Serif 4?

Yes. Drop the PDF into MythosPDF and click the text. New letters are set in Source Serif 4 itself, loaded from the open font, so the edit matches the rest of the page.

+Is Source Serif 4 free to use?

Source Serif 4 is released under the SIL Open Font License 1.1, an open licence that allows free use in documents, including commercial ones. Check the licence text for your exact use.

+Which font is closest to Source Serif 4?

By measured letter widths, Noto Serif HK is the closest match among open fonts (a mean difference of 16.3 units per 1000 em). Text set in one takes almost the same space in the other.

+Which languages does Source Serif 4 support?

It includes these character sets: Cyrillic, Cyrillic Extended, Greek, Latin, Central European, Vietnamese.

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