Highlight & Emphasize
Use rectangles, ellipses, and arrows to draw attention to important details in screenshots, photos, and diagrams.
Image Annotator
Annotate images online for free — draw shapes, add text, blur faces, redact info and highlight screenshots. Browser-based, no uploads, no sign-up.
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An image annotator lets you draw shapes, add text, highlight areas, and blur sensitive information on images. It's used for creating tutorials, providing feedback on designs, redacting personal information, and marking up screenshots. This tool uses the Canvas API for all drawing operations -- no images are uploaded, making it safe for confidential or sensitive visual content.
Annotate and redact images without uploading them
Draw shapes, arrows, text, and pixelate sensitive areas. Full undo/redo history. All processed locally in your browser — no uploads, no sign-up.
Full toolkit
Redact sensitive info
Free unlimited
How to use
- 1
Upload Your Image
Click the upload area or drag and drop an image file to load it into the editor.
- 2
Select a Tool
Choose a tool from the toolbar, such as Rectangle, Arrow, Pen, Text, or Mosaic.
- 3
Customize Settings
Adjust the color, line width, font size, or mosaic pixel size to fit your needs.
- 4
Annotate the Image
Click and drag on the image to draw shapes, lines, or apply effects. If using the Text tool, click where you want to add text.
- 5
Download Your Work
Once you are finished, click the 'Download Image' button to save the final annotated image as a PNG file to your device.
A Full-Featured Annotation Toolkit
Communicate Clearly
Add text directly onto your images to provide context, labels, or instructions. Perfect for tutorials and feedback.
Redact & Censor
The mosaic tool lets you easily pixelate sensitive information, protecting privacy by obscuring faces, names, or numbers.
Full Undo/Redo
Step back and forth through your annotation history with unlimited undo operations. Keyboard shortcuts supported.
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Understanding Image Annotation
Annotation use cases and techniques
Image annotation is the process of adding visual marks to an image -- arrows, rectangles, circles, text labels, highlights, and blurs -- to draw attention to specific areas or convey additional information. Common use cases include: software tutorials (highlighting buttons and menu items with arrows and labels), design feedback (circling issues and adding comments), bug reports (annotating screenshots with steps to reproduce), and privacy redaction (blurring faces, license plates, or sensitive text).
The technical implementation uses the Canvas API's 2D drawing context. Rectangles are drawn with strokeRect() and fillRect(). Circles and arrows use arc() and lineTo() with stroke(). Text is rendered with fillText() and strokeText(). Highlights use a semi-transparent fill color. Blurring is achieved by drawing the selected region at reduced resolution and scaling it back up, or by applying a CSS filter: blur() to a clipped region. Each annotation is stored as an object in an array, allowing undo/redo and re-rendering.
For privacy redaction, blurring is preferable to solid-color covering because it preserves some visual context (you can still tell there's text or a face) while making the content unreadable. However, blurring is not cryptographically secure -- sophisticated algorithms can sometimes recover blurred text. For truly sensitive information (passwords, Social Security numbers), use solid black rectangles instead of blurs. The blur strength (radius) should be at least 10-15 pixels to prevent recovery.
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Best practices for effective annotations
Use consistent colors for different types of annotations: red for errors or problems, green for correct items, blue for information, yellow for highlights. Keep annotations minimal -- too many marks on an image create visual noise and reduce clarity. Use arrows to point to specific elements rather than circling large areas. Label each annotation with a number or short text so the viewer can follow the sequence.
When creating tutorials, annotate screenshots in the order of the steps. Use callout boxes (text on a colored background with an arrow pointing to the relevant area) for step-by-step instructions. Export the annotated image as PNG (not JPEG) to avoid compression artifacts around text and sharp lines. If the annotated image will be displayed on a high-DPI screen, render at 2x resolution and scale down with CSS for crisp text and lines.
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Common Use Cases
Technical Support
Circle or point to issues in a screenshot to clearly explain a problem.
Education & Tutorials
Create step-by-step visual guides by annotating screenshots with numbers and text.
Design Feedback
Mark up mockups and designs with comments and suggestions for your team.
Privacy Protection
Before sharing photos online, use the mosaic tool to blur out personal information.
How does this compare to other annotation tools?
A side-by-side comparison of popular image annotation tools.
| Feature | NovaTools | Annotely | Marker.to |
|---|---|---|---|
| Privacy (no upload) | 100% browser | Uploads to server | Uploads to server |
| Shapes: rect, circle, arrow | All | Limited | |
| Text labels | |||
| Blur/redact tool | |||
| Undo/redo | |||
| No registration |
Server-based annotation tools require uploading your images -- a concern for screenshots containing sensitive information. Our tool annotates images entirely in your browser using the Canvas API.
FAQ
Is this tool free to use?
Yes, our online image annotator is completely free to use with no limitations or watermarks. There are no premium tiers, no daily usage caps, no sign-up requirements, and no attribution required. You can annotate as many images as you need, as often as you need, for personal or commercial use. The tool is sustained by non-intrusive advertising rather than paywalls. The output images (PNG) are yours to use however you see fit — there are no license restrictions on the annotated images. All annotation features — shapes, text, mosaic blur, arrows, pen drawing — are available without any limitations.
Are my images safe and private?
Absolutely. All annotation and processing happens directly in your web browser using the HTML5 Canvas API. Your images are never uploaded to our servers, stored in a database, or accessible to anyone but you. The tool reads your image from local memory, renders it on a canvas, applies your annotations (shapes, text, mosaic effects) as canvas drawing operations, and exports the result — all without any network requests. When you close the browser tab, all image data and annotation history are cleared from memory. This makes the tool safe to use for confidential screenshots, medical images, legal documents, or any scenario where image data should not be exposed to third parties.
What is the Mosaic tool for?
The Mosaic tool allows you to pixelate a selected area of your image. It works by dividing the selected region into small blocks (configurable pixel size) and replacing each block with the average color of its pixels, creating a blurred, blocky effect. This is perfect for redacting sensitive information like faces, license plates, names, email addresses, phone numbers, or addresses before sharing an image online. Unlike simple blur effects, mosaic pixelation is irreversible — the original pixel data is replaced, so the redacted information cannot be recovered even by sophisticated deblurring algorithms. The tool also offers a solid-color redaction mode for completely hiding information.
Can I undo a mistake?
Yes, you can use the 'Undo' and 'Redo' buttons in the toolbar to easily step back and forth through your changes. The tool maintains a full history stack of all annotation operations, so you can undo as many steps as needed — there is no limit to the number of undo operations. Each annotation (drawing a shape, adding text, applying mosaic) is recorded as a separate history entry. The keyboard shortcuts Ctrl/Cmd+Z (undo) and Ctrl/Cmd+Shift+Z (redo) are also supported for faster workflow. The history is cleared when you load a new image or close the browser tab.
What annotation tools are available?
The tool provides a comprehensive annotation toolkit: Rectangle (for highlighting areas), Ellipse (for circling items), Arrow (for pointing to specific features), Pen/Freehand (for drawing custom shapes), Text (for adding labels, comments, or instructions), Mosaic/Pixelate (for redacting sensitive information), and Line (for drawing straight lines). Each tool has customizable settings: color picker, line width, font size, and mosaic pixel size. You can switch between tools instantly using the toolbar or keyboard shortcuts. All annotations are rendered at full resolution and exported as part of the final image.
Can I annotate a screenshot I just took?
Yes. You can paste a screenshot directly into the tool using Ctrl/Cmd+V (paste). The tool detects clipboard image data and loads it automatically — no need to save the screenshot to a file first. This is especially useful for quick annotations of screenshots captured with system tools like Snipping Tool (Windows), Cmd+Shift+4 (macOS), or screenshot keyboard shortcuts. You can also drag and drop an image file from your file manager, or click the upload area to select a file. The tool accepts PNG, JPEG, WebP, and BMP formats.
What is the output format?
The annotated image is exported as a PNG file, which uses lossless compression to preserve every pixel of the original image plus your annotations. PNG is the recommended format for screenshots and annotations because it preserves sharp edges (text, shapes) without introducing JPEG compression artifacts. If you need a smaller file size (e.g., for email or web upload), you can use our Image Converter tool to convert the PNG to JPEG or WebP after annotation. The output resolution matches the original image resolution — annotations are rendered at full resolution, not rasterized at a lower quality.
Can I use this for professional design feedback?
Yes. The tool is well-suited for design review workflows: upload a mockup or wireframe, use arrows and text to point out specific elements, use rectangles to highlight areas that need changes, and add comments with the text tool. The annotated image can be downloaded and shared with team members or clients via email, Slack, or project management tools. The tool is particularly useful for remote teams who need a quick, no-install way to provide visual feedback on designs without using heavyweight software like Figma, Sketch, or Photoshop.
Your Privacy is Our Priority
This tool runs entirely in your browser using the HTML5 Canvas API.
- We do not upload, store, or analyze your files.
- Everything you process stays on your device.
- The tool reads your image from local memory, renders it on a canvas, applies your annotations (shapes, text, mosaic effects) as canvas drawing operations, and exports the final annotated image — all without any network requests.
- There are no server-side logs capturing your image filenames or annotation contents, no analytics tracking which tools you use or how many annotations you make, and no persistent storage of any kind.
- When you close the browser tab, all image data, annotation history, and undo/redo stacks are cleared from memory immediately.
- This makes the tool safe to use for confidential screenshots, medical images, legal evidence, proprietary product photos, internal mockups, and any scenario where visual data should not be exposed to third-party servers.
- The tool also works offline after the initial page load.
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