Below are a number of online jigsaw puzzle sites. All puzzles have pieces that snap together and make a sound when placed correctly, and the options to change the background colour, piece style and number of pieces.

Jigsaw Planet
The main page is filled with a randomly picked collection of puzzle thumbnails, and may display a plaintive message to please turn the adblocker off. Click on an image and the puzzle loads, filling most of the screen; to make it fill the whole screen, click on "Maximize" at the bottom right. Each puzzle has a default piece style and number of pieces, but clicking on "Play As" lets you change that. The settings at bottom left include a "ghost" button that projects a ghostly version of the puzzle image in the middle of the screen, and an "Arrange" option to neatly lay out the pieces on either side of where this image is projected. The pieces can be rotated, but only if the creator allowed for it when making the puzzle. (To make and submit a new puzzle, you have to create an account.) When the puzzle is completed, the site plays a festive sound.

As the puzzle fills the screen, there's not much room for information or credits; I get to see just the puzzle's title and, unless I've specified a custom number of pieces, the fastest playing time of other players who completed the puzzle.
The JigsawPuzzles would like to be a part of your life, offering to add an icon to your desktop so you'll never have to look for this site again. Between the puzzle thumbnails on display, there are four buttons to download dedicated puzzle software for PC, Mac, Android and iOS, which can apparently download puzzles for offline play. Click on a thumbnail and bam, you're on a page with a screen showing a progress bar while the image is being carved up in the default manner. Don't like it? To the right of the playfield is a little window titled "Actions", the topmost being "Change cut". Or, rather than clicking on a puzzle thumbnail, hover over it and choose the number of pieces. To submit your own puzzle, and apparently also to opt for more than 200 pieces, you have to create an account.

The playfield has a hint button, a "Show Preview" button, a fullscreen button, a menu button that includes the option "Pull pieces apart" which places them at random around the edge of the playfield, and an "Edges Only" button that hides any non-edge piece until all the edge pieces have been put in place, after which all the other pieces automatically reappear. While not in fullscreen mode, to the left of the playfield there is a speech bubble containing the puzzle's title and author, and a collection of small thumbnails from the same puzzle category.

Jigsaw Explorer
One thing this site has that the other puzzle sites don't, is the "Friday mystery puzzle" where the thumbnail shows only part of the image, and the player has to guess the rest. When replaced by the next mystery puzzle, the puzzle goes into the general puzzle archive with a normal thumbnail. On choosing a puzzle, I'll be taken to the puzzle image's very own page, giving me title, date, author and some extra information; at the top of the page is a button, "Play this Puzzle", which, if clicked, opens a new tab for the puzzle playfield. I suspect this is to prevent using unnecessary bandwidth when browsing puzzles, because Jigsaw Explorer is developing an app for mobile devices.

The playfield fills the whole screen, although there is a fullscreen button at the right of the menu bar to make it even bigger, and starts with a floating menu in the centre of the screen that includes the buttons "Choose the number of puzzle pieces" and "Make the puzzle pieces rotatable"; I can't start the puzzle until I click its OK button. To change things mid-puzzle, click on the menu button at the left of the menu bar, and choose "Modify this puzzle". The question mark at the far right shows the helpfile and image information, and the button in the middle makes all except the edge pieces disappear, automatically reappearing when the puzzle's sides are completed. Sadly the pieces, no matter what their style, don't vary much in shape, so that in large areas of the same colour, like a stretch of sky, pieces may seem to fit both shape-wise and image-wise, yet don't. When two pieces that do fit are brought close together, the player is warned by a tiny animation of two jigsaw pieces joining together. Once the puzzle is finished, a row of silhouetted hands along the screen's bottom lengthily cheers and applauds.

Also unique to this site: the menu button has "Open your own file as a puzzle" which lets me choose a local file, like one of the images in "My Pictures" or something from the wallpapers folder, to be loaded into memory, carved up, and played as a puzzle. This doesn't actually create a puzzle, it just lets me use my own images without having to submit them to the site.
As soon as this page loads, a window pops up, asking me to log in. Having an account would let me upload my own puzzle images, but I don't like having to sign up for a site just to surf it. I bypass the popup window by clicking either a puzzle title listed in it or any puzzle thumbnail not obscured by the popup window, which opens that puzzle, and from there I can browse and play other puzzles without problems. Hovering over a thumbnail lets me choose the style and number of pieces. The puzzle playfield is squashed into the top half of the screen, with a menu to change the way the puzzle is cut to the left, and image title, source and additional information below. Also shown below are the fastest playing times of other players.

Uniquely, the pieces, no matter what their style, don't have a 3D look but are flat, and when fitted together, meld seamlessly into each other. Most styles have simple and repetitive shapes, so in puzzles with a big area of the same colour, there is a risk of confusing two pieces that seem identical, but the puzzles are on the small side. Maybe this site would be less of a strain on older computers or slower internet connections?