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Highlight Text in Images & PDFs Online

Upload an image or PDF, scan its text with client-side OCR, and highlight your chosen words or phrases. Your file never leaves your browser.

Limits: 20 MB per file; PDFs process up to the first 15 pages. OCR recognises English text. Large images depend on available browser memory.

Phrases with spaces (like "Social Media") are supported.

What is the KitBox Text Highlighter?

The KitBox Text Highlighter is a free online tool that finds words in an image or PDF and highlights them for you. Instead of marking text by hand in an editor, you type the words or phrases you care about, and the tool scans your file and adds a highlighter-style mark over every match. It is useful for screenshots, scanned pages, photos of documents, invoices, study notes, and social media posts.

How to highlight text in an image

  1. Upload your file. Choose an image (PNG, JPG, WebP, GIF, BMP) or a PDF.
  2. Type the text to highlight. Enter one or more words or phrases, separated by commas.
  3. Pick a color and format. Choose a highlight color and whether you want PNG, JPEG or WebP.
  4. Click "Scan & Highlight Text". Wait a few seconds while the text is read.
  5. Download the result. Save your highlighted image, or each highlighted page if you used a PDF.

Why use this tool?

  • Private by design. Everything runs in your browser. Your image or PDF is never uploaded to a server.
  • Free, with no sign-up. No account, no watermark, no limits on how often you use it.
  • Works on images and PDFs. Highlight text in screenshots, photos and multi-page PDF documents.
  • Highlights phrases too. Mark single words or full phrases such as "Social Media".
  • Keeps text readable. The highlight is blended like a real highlighter, so the words underneath stay clear.

Common uses

  • Students marking key terms in lecture slides and study screenshots
  • Teachers preparing worksheets and reading material
  • Marking important details in invoices, receipts and forms
  • Highlighting key points in screenshots for presentations and reports
  • Calling out keywords on social media graphics and posts

Tips for better results

  • Use a clear, sharp image. Blurry or very small text is harder to read.
  • Check your spelling. The tool matches the words you type.
  • Keep "Tolerate small OCR errors" switched on to catch words that were slightly misread.
  • Dark text on a plain light background gives the most accurate results.
  • The tool reads English text.

Frequently asked questions

Is the Text Highlighter free?

Yes. It is completely free to use, with no sign-up and no watermark on your result.

Is my image or PDF uploaded to a server?

No. All the scanning and highlighting happens inside your own browser. Your file is never sent to KitBox or anyone else.

What file types can I use?

You can use images (PNG, JPG, WebP, GIF, BMP) and PDF files. For a PDF, up to the first 15 pages are processed and each processed page can be downloaded as an image.

Why was a word not highlighted?

The tool reads text with OCR, so blurry, tiny or stylised text can be misread. Check your spelling, use a clearer or larger image, and keep the option to tolerate small OCR errors switched on.

Can I highlight more than one word or a whole phrase?

Yes. Separate words or phrases with commas, for example: Followers, Social Media, 24/7. Phrases are highlighted as one block when they appear on the same line.

Which languages are supported?

The tool currently reads English text.

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