Crop images online: aspect ratios, formats, and tools

Image cropping is a basic editing operation: select the area you need and remove the rest. The right aspect ratio is important for social media, banners, and avatars—each platform has its own requirements.

To crop an image, use Image Crop on reChecker.

Aspect ratios: the basics

An aspect ratio is the ratio of an image’s width to its height. The notation 16:9 means that for every 16 units of width, there are 9 units of height.

Common aspect ratios

1:1 (square)

• Instagram: photos, posts, and avatars
• Telegram: avatars and previews
• LinkedIn: profile photos

4:3 (almost square)

• Standard for older TVs and monitors
• Photos from cameras (often)
• Presentations in the old format

3:2

• DSLR cameras — standard 35 mm frame
• Postcards and photo prints 10×15 cm

16:9 (widescreen)

• YouTube: thumbnails and videos
• Presentations (PowerPoint, Google Slides)
• Modern monitors and TVs
• Banners and social media covers

9:16 (vertical)

• Instagram Reels, TikTok, YouTube Shorts
• Stories on Instagram, VK, and Telegram
• Vertical mobile formats

2:3 and 3:4

• Pinterest — long vertical pins
• Portrait photos

Image sizes for different platforms

Instagram

YouTube

VK

Telegram

LinkedIn

Open Graph (link previews)

When you share a link on social media, the preview is generated from OG tags:

• Recommended size: 1200×630 px (aspect ratio ~1.91:1)
• Minimum: 600×315 px

Check how the preview looks: Open Graph Preview.

The rule of thirds in cropping

The rule of thirds is a basic composition principle: divide the frame into 9 equal parts using two horizontal and two vertical lines. Place the main subject at the intersections of these lines.

+-------+-------+-------+
|       |       |       |
+-------+---X---+-------+  ← объект на пересечении
|       |       |       |
+-------+-------+---X---+
|       |       |       |
+-------+-------+-------+

When cropping a portrait, the eyes should be on the upper horizontal line of the rule of thirds, not in the center of the frame.

How to crop correctly

Portraits

• Leave space above the head (if the person’s eyes are looking upward)
• Don’t crop at the joints (wrists, knees, ankles)
• For an avatar in 1:1, center the face and leave a little space around it

Landscapes

• Place the horizon on the lower third (when the sky dominates) or upper third (when the land dominates)
• Never put it in the center—it looks boring
• Choose 16:9 or 3:2 for wide panoramas

Product photos

• For e-commerce catalogs: white background, 1:1, subject occupies 80% of the frame
• For social media: context and textures add atmosphere, 4:5 or 1:1

Text and banners

• Leave a “safe zone” around the edges—10% from each side
• Third-party platforms may crop the edges when displaying the image

Quality when cropping

Cropping itself does not reduce quality—you are simply selecting part of the image. Quality can decrease only when:

1. Saving as JPG at low quality — compression artifacts
2. Upscaling — if the cropped area is smaller than the target size, the pixels are stretched

Tip: if you need a 200×200 px thumbnail for an avatar, it’s better to crop it from an image that is 600×600+ pixels, rather than upscale a 200×200 crop.

Formats when saving

PNG

• Lossless quality
• Supports transparency
• Larger file than JPG
• Use for logos, screenshots, and images with transparency

JPG

• Small file at good quality (85–90%)
• Does not support transparency
• Use for photos and social media posts

Batch cropping (programmatic)

For websites with large numbers of images, automate cropping:

Sharp (Node.js)

const sharp = require('sharp');

// Обрезка квадрата из центра
await sharp('photo.jpg')
  .resize(800, 800, {
    fit: 'cover',
    position: 'center'
  })
  .toFile('avatar.jpg');

// Обрезка определённой области
await sharp('photo.jpg')
  .extract({ left: 100, top: 50, width: 400, height: 400 })
  .toFile('cropped.jpg');

Python (Pillow)

from PIL import Image

img = Image.open('photo.jpg')

# Обрезка по координатам (left, top, right, bottom)
cropped = img.crop((100, 50, 500, 450))
cropped.save('cropped.jpg')

# Квадратная обрезка из центра
width, height = img.size
size = min(width, height)
left = (width - size) // 2
top = (height - size) // 2
square = img.crop((left, top, left + size, top + size))
square.save('avatar.jpg')

CSS: object-fit

To crop images in the browser without editing the file:

.thumbnail {
  width: 200px;
  height: 200px;
  object-fit: cover;     /* обрезает под контейнер */
  object-position: top;  /* выравнивание: top, center, bottom */
}

// Next.js Image с fill и object-fit
<div style={{ position: 'relative', width: 200, height: 200 }}>
  <Image src="/photo.jpg" alt="..." fill style={{ objectFit: 'cover' }} />
</div>

Online cropping tools

Image Crop on reChecker — visual cropping with preset aspect ratios, pixel dimensions displayed, and export to PNG or JPG. Everything runs in the browser—the image is not uploaded to a server.

Other image tools:

• Image Resize — resize images
• Image Compressor — compression without quality loss

Conclusion

Correct cropping means choosing the right part of the image and the right aspect ratio for the platform. For Instagram Stories, use 9:16; for YouTube thumbnails, 16:9; for avatars, 1:1. Use Image Crop to crop images quickly right in your browser.