Cannot identify image file

PIL.UnidentifiedImageError: cannot identify image file

Look at the first bytes

with open("photo.jpg", "rb") as fp:
    print(fp.read(16))

What you see tells you what you really have:

The usual causes

• A download that returned HTML. Rate limiting, a login page or a 404 saved with an image name. Check the status code and the content type before writing the file.
• Reading a stream twice. A file object or BytesIO that has already been read is at the end. Call fp.seek(0) first.
• A format Pillow cannot read. HEIC from iPhones needs pip install pillow-heif. Some TIFF and RAW variants need extra plugins.
• An SVG. It is a text format, not a bitmap. Pillow does not read it. Use cairosvg to rasterise first.

Reading from bytes properly

from io import BytesIO
from PIL import Image

buffer = BytesIO(data)
buffer.seek(0)
im = Image.open(buffer)

Still stuck

The PIL to Pillow converter finds most of these automatically, and the other error pages cover the rest.