When text is placed in InDesign, the type is automatically situated in the text frame based on the defined edges of the frame and the justification setting of the text (left, right, center, justified, etc.). Most of the time this looks fine, but when certain characters are the first character of a line, the nice, even flow of the margin edge will be interrupted.

The result is a slight variation in the left margin. If we look at the visual weight of the lines of text it becomes more obvious:

Indentations are usually a visual cue that we’re starting a new paragraph, and even though you probably won’t confuse anyone with a slight indention like this, it could be enough to add a visual hiccup to your reader’s ability to flow effortlessly from one line to the next. Luckily, InDesign can compensate for this using the Optical Margin Alignment setting in the Story panel.

You can find the Story panel under Window>Type & Tables>Story. Turning on OMA is as easy as clicking the box next to…you guessed it: “Optical Margin Alignment.” The results look like this:

Notice how the quotation marks now overlap the text frame allowing the “i” to become the de facto first character on the line.

You can control the amount of margin alignment with the other set of controls in the Story panel. (This will be set at 12pt automatically). This setting only needs to be activated once per story, and just for the record: a “story” is a text box, or a set of linked text boxes with copy flowing between them.

OMA will help to compensate for glyphs like quotation marks (as in the example images) as well as round letterforms and letterforms such as “W” and “T” that have a lot of natural white space in the lower left quadrant of the glyph.