Some Useful After Effects Expression for Editing Text Proporties

Setting multiple features:

// Retrieve font size value from a slider control named "Font Size"
var s = effect("Font Size")("Slider").value;

// Get the existing TextDocument from the Source Text property
var t = text.sourceText;

// Modify the text style by chaining style methods:
// - .setFont("Montserrat-Light") sets the default font.
// - .setFont("Gigantic", 0, 6) applies the "Gigantic" font to characters from index 0 for 6 characters.
// - .setFont("Gigantic", 10, 6) applies it for characters starting at index 10 for 6 characters.
// - .setFont("Gigantic", 20) applies it from index 20 to the end of the text.
// - .setFontSize(s) sets the font size based on the slider value.
// - .setLeading(80, 0, 30) sets the leading (line spacing) to 80 for characters starting at index 0 covering 30 characters.
var newText = t.style
    .setFont("Montserrat-Light")    // Default font for the text layer
    .setFont("Gigantic", 0, 6)        // Apply "Gigantic" font to first 6 characters
    .setFont("Gigantic", 10, 6)       // Apply "Gigantic" font to characters 10 to 15
    .setFont("Gigantic", 20)          // Apply "Gigantic" font from character 20 onward
    .setFontSize(s)                 // Set the font size from the slider control
    .setLeading(80, 0, 30);          // Set leading (line spacing) to 80 for characters 0 to 30

newText;

// Retrieve font size value from a slider control named "Font Size"
var s = effect("Font Size")("Slider").value;

// Get the existing TextDocument from the Source Text property
var t = text.sourceText;

// Modify the text style by chaining style methods:
// - .setFont("Montserrat-Light") sets the default font.
// - .setFont("Gigantic", 0, 6) applies the "Gigantic" font to characters from index 0 for 6 characters.
// - .setFont("Gigantic", 10, 6) applies it for characters starting at index 10 for 6 characters.
// - .setFont("Gigantic", 20) applies it from index 20 to the end of the text.
// - .setFontSize(s) sets the font size based on the slider value.
// - .setLeading(80, 0, 30) sets the leading (line spacing) to 80 for characters starting at index 0 covering 30 characters.
var newText = t.style
    .setFont("Montserrat-Light")    // Default font for the text layer
    .setFont("Gigantic", 0, 6)        // Apply "Gigantic" font to first 6 characters
    .setFont("Gigantic", 10, 6)       // Apply "Gigantic" font to characters 10 to 15
    .setFont("Gigantic", 20)          // Apply "Gigantic" font from character 20 onward
    .setFontSize(s)                 // Set the font size from the slider control
    .setLeading(80, 0, 30);          // Set leading (line spacing) to 80 for characters 0 to 30

newText;

Here are some other settings:

Here are the set of functions available for text styling in After Effects expressions (all used on the style object):

These functions can be chained together to modify multiple style attributes at once—for example:

jsCopy codetext.sourceText.style
  .setApplyFill(true)
  .setFillColor(hexToRgb("FFFFFF"))
  .setBaselineShift(10)
  .setTracking(25)
  .setAutoLeading(true);

✅ Basic Styling (from Adobe Help)

• setFont(fontName, [startIndex], [endIndex])
• setFontSize(size, [startIndex], [endIndex])
• setFauxBold(boolean, [startIndex], [endIndex])
• setFauxItalics(boolean, [startIndex], [endIndex])
• setAllCaps(boolean, [startIndex], [endIndex])
• setSmallCaps(boolean, [startIndex], [endIndex])
• setTracking(value, [startIndex], [endIndex])
• setLeading(value, [startIndex], [endIndex])
• setAutoLeading(boolean)
• setBaselineShift(value, [startIndex], [endIndex])
• setStrokeWidth(value, [startIndex], [endIndex])
• setApplyFill(boolean)
• setFillColor(colorArray, [startIndex], [endIndex])
• setApplyStroke(boolean)
• setStrokeColor(colorArray, [startIndex], [endIndex])
• setText(textValue) — set the text content via style object

✨ Advanced & Per-Character / Paragraph Styling (new in AE 25+)

These are documented in the expanded Text Style API ae-expressions.docsforadobe.dev+11ae-expressions.docsforadobe.dev+11ae-expressions.docsforadobe.dev+11ae-scripting.docsforadobe.dev+3ae-expressions.docsforadobe.dev+3ae-expressions.docsforadobe.dev+3:

• Per-character styling (accepts optional startIndex, endIndex):
  • setHangingRoman(boolean)
  • setHorizontalScaling(value)
  • setJustification(option)
  • setKerning(value)
  • setKerningType(type)
  • setLeadingType(type)
  • setLeftMargin(value)
  • setLigature(boolean)
  • setLineJoin(type)
  • setRightMargin(value)
  • setSpaceAfter(value)
  • setSpaceBefore(value)
  • setTsume(value)
  • setVerticalScaling(value)
  • setDigitSet(option)
  • setBaselineDirection(option)
  • setBaselineOption(option)
  • replaceText(newText, [startIndex], [endIndex])
• Paragraph-specific methods (apply to entire layer):
  • setDirection(direction) — e.g. “ltr” or “rtl”
  • setEveryLineComposer(boolean)
  • setFirstLineIndent(value)
  • setHangingRoman(boolean) — also listed above
  • setJustification(option)
  • setLeadingType(type)
  • setLeftMargin(value)
  • setRightMargin(value)
  • setSpaceAfter(value)
  • setSpaceBefore(value)

These additions provide fine‑grained typographic control—covering spacing, directionality, indentation, margins, kerning, ligatures, line joins, typographic scaling, and even Venetian typographic styles like hanging roman punctuation ae-expressions.docsforadobe.dev+2ae-expressions.docsforadobe.dev+2ae-expressions.docsforadobe.dev+2helpx.adobe.com+2helpx.adobe.com+2motiondeveloper.com+2ae-expressions.docsforadobe.dev.

🧩 Summary Table: All TextStyle set… Methods

Quick Tip:

If you want to retrieve currently used font’s name you can use the following expression:
text.sourceText.style.font