You place a logo on a coloured slide and a white rectangle appears around it. Or the edges of a sticker look jagged and grey after you convert it. Both problems come from the same place: transparency, and the fact that not every image format handles it the same way. This guide explains what transparency is, which formats support it, and how to convert images without losing clean edges.
What transparency means
Every pixel in an image has a colour. Formats that support transparency also store how opaque each pixel is: fully solid, fully see-through, or somewhere in between. That extra information is called the alpha channel.
- Alpha fully opaque: the pixel's colour is shown normally.
- Alpha fully transparent: the pixel is invisible; whatever is behind it shows through.
- Alpha partly transparent: the pixel is blended with what is behind it.
Partial transparency is what makes edges look smooth. When a round logo is drawn, the pixels along its curved edge are partly transparent, so they blend gently into any background instead of forming a staircase of hard pixels.
Which formats support transparency
- PNG: full, smooth transparency. The classic choice for logos and icons.
- WebP: full, smooth transparency in both lossy and lossless modes.
- AVIF: full, smooth transparency.
- TIFF: supports transparency, mainly used in professional workflows.
- GIF: only on-or-off transparency. Each pixel is either fully transparent or fully solid.
- JPG: no transparency at all.
- BMP (standard 24-bit): no transparency.
What happens when you convert to a format without transparency
If the target format cannot store transparency, the transparent areas must be filled with a solid colour. Our converters handle this openly:
- They detect transparency when you upload.
- They tell you that transparent areas will be filled.
- They let you choose the background colour, with white as the default.
The trick is choosing the right colour. If your JPG will sit on a white web page, white is perfect. If it will go on a navy banner, choose navy. The partly transparent edge pixels are blended with your chosen colour, so the edges look smooth against that colour specifically.
Why edges sometimes look jagged or haloed
Converting to GIF
GIF only allows fully transparent or fully solid pixels. Partly transparent edge pixels must be rounded one way or the other. The result can be slightly jagged edges, especially on curves and soft shadows. Our converter warns you when your image has semi-transparent pixels before you convert to GIF.
Filling with the wrong colour
If you fill a logo's transparent background with white, and then place the resulting JPG on a dark background, the edge pixels, which were blended with white, look like a pale outline. That is a halo. The fix is to convert with a background colour matching the final destination, or to keep the image in a format with transparency.
Images designed for one background
Some images were originally drawn on a particular colour, with the edges blended to that colour before the background was removed. Placing them on a very different colour reveals a faint fringe. Using the original artwork, or a version designed for transparency, avoids this.
Practical recipes
A logo for websites
Use PNG to WebP with lossless on. You keep perfect transparency and save space.
A logo for slides and documents
PNG works almost everywhere. If you received a WebP or AVIF logo, convert with WebP to PNG or AVIF to PNG.
A logo for an upload form that only accepts JPG
Use PNG to JPEG and choose a background colour that matches where it will be shown.
A sticker for a chat app that only supports GIF
Use PNG to GIF. If edges look jagged, design the sticker with a solid outline, which survives the on-or-off transparency of GIF well.
A worked example: one logo, three destinations
A community choir has a round logo with a soft shadow, saved as a transparent PNG. They need it in three places.
- Their website. They convert it with PNG to WebP using lossless mode. The shadow and smooth edges stay perfect, and the file is smaller.
- A printed concert programme, created in software that only accepts JPG. The programme pages are cream-coloured, so they convert with PNG to JPEG and choose a cream background colour. The logo's soft edges blend perfectly into the page.
- A chat sticker for members. The chat app only animates and displays GIF stickers, so they convert to GIF. The soft shadow becomes a harder edge. They decide it looks better without the shadow, remove it from the original, and convert again for a crisp result.
Same logo, three formats, each chosen for where it is going.
Why designers love PNG and WebP
Designers often deliver logos as transparent PNG or WebP files precisely so they can be placed on any background without extra work. If you receive a logo as a JPG with a white box, ask whether a transparent version exists. It will save you time with every future design.
How to check transparency is really there
Many image viewers show transparent areas as white or as a grey checkerboard pattern. If you are unsure whether an image is transparent, place it over a coloured shape in a slide or document. If the colour shows through, the transparency is there.
Common questions
My PNG has a white background. Is it transparent? Not necessarily. A PNG can be fully opaque with a white background. Transparency has to be in the image itself.
Can converting add transparency? No. Converting to PNG gives you a format that can hold transparency, but removing a background requires editing software.
Why do shadows look grey and blocky after converting to GIF? Soft shadows are made of partly transparent pixels, which GIF cannot represent. Use PNG or WebP to keep them.
Will a transparent image look the same in every app? Formats with full alpha support will look the same; how an app displays the transparent areas, white, checkerboard or the page colour, varies.
In short
Transparency is stored in an alpha channel that PNG, WebP, AVIF and TIFF support fully, GIF supports only partially, and JPG and BMP do not support at all. When converting to a format without transparency, choose a background colour that matches the destination. When you need smooth, see-through edges, stick with PNG or WebP. Following those rules eliminates white boxes and halos for good.