# Resize an Image for Social Media

> Make a picture square, portrait or landscape for a feed: pick a frame, keep the whole picture or crop to the part you want, and save the file. Made on your device.

- Canonical: https://prisment.io/blog/resize-an-image-for-social-media/
- Published: 2026-10-07
- Checked against: Prisment v2.0.6
- Author: Prisment Team (Documentation & Developer Tooling)
- Publisher: Prisment, https://prisment.io/

**You resize an image for social media in Prisment by opening it, pressing Convert, picking Square, Portrait or Landscape under Frame and saving the file.** The picture is made on your device, never uploaded, and you see the exact file before you download it.

## 1. Which sizes does it make?

**Three frames, in sizes feeds commonly show: square, portrait and landscape.**

| Frame | Pixels | Shape |
| :--- | :--- | :--- |
| Square | 1080 × 1080 | 1:1 |
| Portrait | 1080 × 1350 | 4:5 |
| Landscape | 1920 × 1080 | 16:9 |

They are the frames Prisment already uses when you share a Mermaid diagram, so a post made from a screenshot and one made from a diagram match. Platforms change their guidance, so treat the sizes as common starting points and check the one you post to. **Original** keeps the picture's own proportions: that is where its Scale and its width and height are.

## 2. How do you frame a picture?

**Open the picture file, press Convert, and pick a frame in the dialog.** It works for a PNG, JPG, WebP, GIF or SVG that you opened in a folder or dropped onto the page.

1. **Open the picture.** It opens in the image viewer.
2. **Press Convert.** One dialog opens: the picture on the left, its options on the right.
3. **Pick a frame** under **Frame**, and a format: PNG, JPG or WebP.
4. **Choose how the picture sits** in it, and what goes around it (the next two sections).
5. **Check the preview and press Save.**

The same dialog holds everything else Convert does: a vector at 1×, 2× or 3×, any width and height, a quality for JPG and WebP, and **Download original**, which hands you the file as it is.

Every option is in the guide's [Framing a picture for social media](https://prisment.io/help/#framing-a-picture-for-social-media) chapter.

## 3. Whole picture, or crop to the part you want?

**Whole picture keeps every pixel with room around it; Crop lets you place the picture in the frame, choosing the part that shows.**

![A wide picture, then the same picture in a portrait frame two ways: whole, with room around it on a grey ground, and cropped, covering the frame with the part you drag into it, a double arrow across it.](https://prisment.io/images/blog/frame-images-fit.png)

Use **Whole picture** for a screenshot, a chart, a logo or a diagram, where a cut-off edge loses something. The room around it is 7 % of the frame's shorter side, the same margin a shared diagram gets.

Use **Crop** when only part of the picture is the point: one block of a screenshot, the face in a photo. **Drag the picture** to move the part that shows, and move **Zoom**, from 10 to 400 %, to show less of it. At 100 % the picture just covers the frame; above it you see less, and below it the picture is smaller than the frame and sits on the Background, where you can move it about. The arrow keys move it too, Shift further, and **Centre** puts both back. The part outside the frame shows faintly, so you can see what is being cut away.

![The Export picture dialog set to Square and Crop at 200 percent zoom: on the left the picture shown faintly with a bright square window over one block of it, on the right the formats, frames, Fit, the Background, a Zoom slider with a Centre button below it, and Save.](https://prisment.io/images/blog/frame-images-crop.png)

## 4. What goes around the picture?

**You choose the ground wherever the picture does not reach the frame: Light, Dark, None, or a colour of your own.** That is room round a whole picture, and round a crop zoomed out below 100 %. Light and Dark are the two grounds the viewer's Background menu already offers. Colour… opens the system colour picker, which is the way to match a brand.

**None** leaves the room around the picture see-through, which a PNG or a WebP can be. A JPG cannot, so for a JPG Prisment fills it and does not offer None. The dialog shows the difference on a checkerboard, the usual sign for "see-through here".

## 5. Do you see the file before you save it?

**Yes: the preview is the file itself.** It is made by the same encoder, with the same options, that makes the download, and the size in pixels and the weight are under it. Change a frame, a fit or a ground and the file is made again.

![The Export picture dialog set to PNG, Portrait, Whole picture on a Dark ground: on the left a wide week view centred in a tall dark frame with the file's size under it, on the right the options and the name it downloads as.](https://prisment.io/images/blog/frame-images-dialog.png)

The file is named after the picture and the frame: `week.svg` framed as a portrait downloads as `week-portrait.png`. Nothing is uploaded, and the original is never changed.

## 6. What does it not do?

**It does not add text or make a tall 9:16 Story frame.** A crop is a window of the frame's own shape: there is no free-form selection, and no rotation. A small picture is enlarged to fit its frame, which softens it, so start from the largest version you have. And nothing is added to the picture: no caption, no watermark, no mark of Prisment's.

## 7. What about a diagram, or a picture in a document?

**A Mermaid diagram has the same frames in its own Share dialog**, as a looping GIF, a PNG or an SVG; the [animated Mermaid diagrams](https://prisment.io/blog/animated-mermaid-diagrams/) article shows it. To size a picture *inside* a document instead, see [resize and align images in Markdown](https://prisment.io/blog/resize-and-align-images-in-markdown/).

## Questions this article answers

### What size should an image be for social media?

Prisment makes three frames: square at 1080 by 1080 pixels, portrait at 1080 by 1350 (4:5) and landscape at 1920 by 1080 (16:9). They are common sizes for feeds, but platforms change their guidance, so check the one you post to.

### How do I make an image square without cropping it?

Open the picture, press Convert, pick Square under Frame and keep Whole picture. The picture is placed in the middle with room around it, on a light, dark or colour ground you choose, and nothing is cut off.

### Can I keep a transparent background?

For a PNG or WebP, yes: choose None as the background and the room around the picture stays see-through. A JPG cannot be see-through, so Prisment fills it instead and does not offer None for that format.

### Is my image uploaded anywhere?

No. The browser draws the framed picture on a canvas on your device and saves the file from there. The original file is never changed and no mark of Prisment’s is added to the picture.

### Can I crop a picture to just part of it for a square post?

Yes. Open the picture, press Convert, pick Square under Frame and press Crop. Drag the picture to choose the part that shows and move Zoom to show less of it. The preview moves as you drag, and the file you save is that same window.

### Can I make a 9:16 Story size?

Not yet. The frames are square, portrait and landscape; a tall Story or Reel frame is not one of them.