# Placeholder Generator — Generate BlurHash placeholders on Mac

Make BlurHash strings, tiny blurred thumbnails and average colours to show while images lazy-load. Part of OneMacTools, 151 private tools in one native Mac app (macOS 26 or later); category: Images. Runs on your Mac; nothing is uploaded.

For each image, get a BlurHash string (with the detail level you choose), a tiny Base64 thumbnail and the average colour, ready to store next to the image's address and show while the real image loads. A preview of each decoded BlurHash is saved alongside.

Page: https://www.onemactools.com/tools/placeholder-generator · Download: https://www.onemactools.com/download · Pricing: https://www.onemactools.com/pricing

## How to use it
1. **Drop your images.** Add the images your site or app will lazy-load, one or many.
2. **Choose the detail.** 4 × 3 suits most images. More detail gives a closer blur but a longer string.
3. **Choose the extras.** Turn on the tiny Base64 thumbnail and the average colour if you want them as well as the BlurHash.
4. **Click Generate.** Every value is listed in the app and saved as Placeholders.txt, with a preview of each decoded BlurHash, in a dated folder in Downloads › OneMacTools.
5. **Store the values with your images.** Save each string next to the image's address in your database or content files, and show it while the real image loads.

## Options
- **BlurHash detail:** 4 × 3 (recommended), 3 × 3, 5 × 4, 6 × 4 or 9 × 9. The number of colour components across and down. Higher values capture more of the image's shape; 4 × 3 gives a 28-character string.
- **Tiny blurred thumbnail (Base64):** On by default. A tiny JPEG, at most 16 px on its longest side, as a data URI you can put straight into an <img> tag or CSS and stretch with a blur.
- **Average colour:** On by default. One hex colour per image, worked out as the average of the whole image, for a plain background while it loads.

## Tips
- Match the detail to the image's shape: 4 × 3 or 5 × 4 for landscape photos, 3 × 3 for square or portrait ones.
- Use the average colour as the background of the image's container; it's the lightest placeholder and needs no decoding.
- Set the image box's width and height to match the real image, so the page doesn't jump when it loads.
- Look at the saved previews to see what people will actually see before choosing a detail level.
- Regenerate the placeholder whenever you replace an image, or the blur won't match.

## Questions
**What is a BlurHash?**
A short text string that encodes a blurred version of an image. Your app decodes it into a soft, colourful placeholder while the real image downloads.

**How do I generate a BlurHash for my images?**
Drop them onto Placeholder Generator and click Generate. Each image gets a BlurHash string in the app and in Placeholders.txt.

**Which BlurHash detail should I use?**
4 × 3 is a good default and gives a 28-character string. Use more components for more shape, at the cost of a longer string.

**Should I use a BlurHash or a tiny thumbnail?**
A BlurHash is short and needs a small decoder in your app. The tiny thumbnail is a data URI that browsers can show directly, but it's a longer string. You can generate both and choose.

**How do I use the average colour?**
Set it as the background colour of the image's container. It shows instantly and matches the image's overall tone.

**Why add placeholders at all?**
They avoid blank boxes and layout jumps while images load, which makes pages and apps feel faster.