Annotating a screenshot so people understand it

A screenshot is one of the fastest ways to explain something: "click here", "this is the error", "this number is wrong". Annotated badly, it becomes a puzzle — arrows pointing at each other, circles around half a button, text that is too small to read.

Good annotation is mostly restraint.

The tools already on your Mac

Screenshot Markup. Take a screenshot with Shift-Command-4 (a selection) or Shift-Command-3 (the whole screen). A thumbnail appears in the corner for a few seconds; click it to open a Markup window before the file is even saved.

Preview. Open any image and click the Markup button (a pen tip in a circle), or press Shift-Command-A. The Markup toolbar appears.

Both give you the same tools:

• Shapes — rectangles, ovals, lines, arrows, speech bubbles and stars.
• Loupe — a magnifying circle to enlarge a small detail.
• Highlight — a translucent box that draws attention without hiding what is under it.
• Text — typed labels, with font, size and colour.
• Sketch and Draw — freehand, with Sketch tidying rough shapes into clean ones.
• Shape Style, Border Color and Fill Color — thickness and colours.

For most everyday annotation, this is enough.

The rules

One point per annotation. Each arrow, box or number should mean one thing. If you need to explain three things, use three numbered markers and explain them in the message.

Boxes beat arrows. A rectangle around a button is unambiguous. An arrow has to be read — where is its tip? — and can point at the wrong thing if the layout shifts.

Crop first. Nobody needs your whole screen to see one button. Crop to the relevant area plus a little context. The annotation gets proportionally larger, and so does everything else.

One colour for pointing. A single strong colour — red or a bright orange — used for every mark. A rainbow of annotations reads as noise.

Make text large. Labels should be readable on a phone without zooming. If the text is small next to the interface text, it is too small.

Number steps. For a sequence, numbered circles — 1, 2, 3 — placed next to the controls beat arrows with sentences.

Leave the interface readable. Do not cover the thing you are pointing at. A box around it, a highlight over it, or a number beside it.

Hiding private information properly

Screenshots routinely contain things they should not: email addresses, names in a sidebar, account numbers, notifications, open tabs.

Crop it out where possible. Nothing is safer than pixels that are not in the file.

Cover it with a solid, opaque shape. In Markup, a rectangle with a solid fill colour — not a highlight, not a border. After saving as a new image, the pixels underneath are replaced.

Avoid blur and pixelation for text. Blurred or pixelated text can sometimes be reconstructed, especially when the font is known and the text is short, like a number. A solid box has no such weakness.

Watch out in PDFs. A shape drawn on a PDF in Preview may sit on top of text that is still in the document and can be selected and copied. For PDFs, use a proper redaction tool — Preview has Tools → Redact — and check the result by trying to select the text.

Check the whole image. Menu bars, notification banners, browser tabs, bookmarks and window titles leak the most.

Before you send

• Is the point obvious within two seconds?
• Does every mark mean one thing?
• Is anything private still visible, including at the edges?
• Is it the right format? PNG for screenshots — it keeps text sharp — unless file size is a real problem.

When Markup is not enough

Markup is good for a quick annotation and less good when:

• You need to come back and change a label, move an arrow or fix a typo after saving.
• You are producing a series of annotated screenshots for documentation and want them consistent.
• You want to combine several screenshots into one image, side by side, with labels.

At that point, the screenshot and the annotations need to be separate, editable pieces.

What Miyu Paint does

Miyu Paint is a native image editor for Mac. The free tools cover what a quick annotation needs — open, crop and resize the screenshot, draw with brushes and pencils, fills and selections — and export PNG or JPEG up to 2048 pixels on the longest edge, without a watermark.

For documentation work, full access adds editable text and shapes on their own layers, so labels and boxes stay changeable after saving, and group layers keep a set of annotations together. Saving as an editable .mpaint project means next month's updated screenshot can go underneath the same annotations. Full access comes from a fourteen-day trial that you start yourself and that never renews into a charge, or a one-time Lifetime Unlock.

Everything happens on your Mac — which matters for screenshots containing private information — with no account, advertising, analytics or tracking.