How to annotate a screenshot on Mac

What macOS's Markup gives you

The free route: Markup in Preview

Preview's Markup toolbar carries a Sketch tool for freehand drawing; a Shapes menu of lines and arrows, rectangles, ovals, speech bubbles, stars and more, with a highlight and a magnifying loupe; a Text tool; and a Sign tool that captures a signature from the trackpad, the Mac's camera, or an iPhone or iPad. Apple's guide to annotating an image lists no redaction tool: Preview's Redaction tool works on text in PDFs, so on a screenshot you cover an area with a rectangle that has a solid fill.

• Take the screenshot: ⇧⌘3 for the whole screen, ⇧⌘4 for a region, or ⇧⌘5 for the on-screen capture controls. See Apple's screenshot shortcuts.
• Click the thumbnail in the corner before it disappears, a few seconds later, to open Markup directly. Missed it? Open the saved file in Preview instead and click the Markup icon (a pen tip in a circle) at the right of the toolbar.
• Pick a tool from the row that appears: Sketch, Shapes, Text, or Sign, and draw. Shape Style sets the thickness and type of a line, and Border Color and Fill Color, separate buttons, set its colors.
• Press ⌘S to save. This is the step that matters: once saved, the marks are part of the image's pixels, not separate objects, so there's nothing left to select afterward.

Where Markup stops

Markup is genuinely capable for a one-off arrow or a circled typo, but it wasn't built for annotation as an ongoing habit. Once a file is saved, its shapes are pixels: reopening it later gives you an image, not a set of editable objects, so fixing a mistyped label or repositioning an arrow means drawing over the old one rather than moving it. Apple's own workaround is to convert the image to a PDF before annotating, where the marks stay editable, which leaves you with a PDF rather than an image. (A filled rectangle used to cover something is flattened the same way; covering sensitive details safely has its own guide, how to redact a screenshot on Mac.) Apple's guide also lists no numbered-callout tool for a step-by-step guide, and there is no library of past marked-up shots to search through. For an occasional edit that's a fair trade for a tool that ships free with every Mac; for anything done often, it adds up.

Annotate and redact together: Snapline

Snapline's annotation editor opens from the Edit action on any capture's Quick Access card (or after every capture, if you switch on Settings → General → After capture → Open Annotate tool) and on any image you open in it: pen, highlighter, line, arrow, rectangle, ellipse, polygon, and star (3 to 12 sides), emoji stickers, text, numbered counter badges, and a crop tool with rule-of-thirds guides. Every mark is stored as a vector, not baked into the pixels, so reopening a shot from History later still lets you nudge, restyle, or delete anything you drew, including weeks after the capture. Clicking Done saves the marked-up image and, by default, puts it on the clipboard ready to paste (Settings → General → After annotating).

Redaction lives in the same toolbar rather than a separate app: the Redact tool covers a selection with pixelation (the default), blur, or a solid box (the one style image analysis cannot reverse), and Smart Redact scans the whole capture on device for emails, phone numbers, URLs, card numbers, IBANs, API keys, and similar, and covers each match automatically. Because annotations and redactions are separate objects in Snapline's editor, they don't have to be all-or-nothing: point an arrow at a field, cover the field itself, and later delete just the redaction for an internal copy while the arrow stays put, or the other way around. A capture's Quick Access card also has a one-click Redact action for the common case: run Smart Redact and bake the boxes in immediately, reversibly, since a second press brings the original back. What you copy, save, or share is the flattened, redacted image; Snapline keeps the un-redacted original on your Mac, which is what makes a redaction removable later.

Annotation isn't limited to fresh captures. PNG, JPEG, TIFF, and HEIC files open in the same editor through Finder's Open With, a drop on Snapline's menu-bar icon (or on its Dock icon, which it shows only while one of its windows is open), or File → Open (⌘O); an imported image joins History like any capture, with the same searchable text recognition and the same re-editable annotations. Snapline is free to try in full for 14 days (after the trial, capture unlocks with a one-time license: no subscription, no account) and requires macOS 14 or later. Screen Recording is needed for capturing a fresh screenshot; opening and annotating an existing image file asks for no extra permission.

Questions

Does Mac have a built-in way to annotate a screenshot?

Yes. Click the thumbnail that appears right after a ⇧⌘3, ⇧⌘4, or ⇧⌘5 capture, or open any image in Preview and click the Markup icon, to draw shapes, arrows, text, and a signature onto it for free. No extra app.

How do I add an arrow to a screenshot on Mac?

In Markup, click Shapes and choose the line with an arrowhead, then drag it into place; Shape Style changes the line's thickness and type. Snapline has a dedicated Arrow tool in its annotation toolset, drawn with one drag.

Can I edit a screenshot's annotations after I've saved the file?

Not in a saved image file: Apple's guide says you can't edit, move, or delete the annotations after you save the image, and suggests converting it to a PDF first if you will need to change them later. In Snapline, annotations are stored as vectors and stay re-editable whenever you reopen the shot, even weeks later.

What's the difference between annotating and redacting a screenshot on Mac?

Annotating adds information, like an arrow or a note; redacting hides information by covering it. Markup has no redaction tool for images (Preview's Redaction tool works on text in PDFs), so the free way is a rectangle with a solid fill, which becomes part of the pixels when you save. Snapline treats annotation and redaction as separate objects in the same editor, so either can be added or removed on its own, and Smart Redact can find what to cover automatically. A solid box is the one cover image analysis cannot reverse; pixelation and blur can sometimes be undone.

Can I number my annotations for a step-by-step guide on Mac?

Not with Markup: Apple's guide lists no counter tool. Snapline's annotation editor has a numbered counter badge for exactly this: click to place badge 1, click again for badge 2, and so on.

Can I annotate an image that isn't a fresh screenshot, like a photo someone sent me?

Yes, in both tools. Preview's Markup opens most image types you already have. Snapline annotates PNG, JPEG, TIFF, and HEIC files opened with File → Open, Finder's Open With, or a drop on its menu-bar icon (or on its Dock icon, which Snapline shows only while one of its windows is open); the imported image joins History like any capture. Neither annotates a PDF's pages the same way; Preview's Markup does work on PDFs directly, but Snapline's editor is images only.