Staff edit: For the most up-to-date information, please see the Sites and Sources wiki page.[/b]I see a fair amount of users uploading smaller or lesser-quality versions of images from Pixiv, Tumblr or Twitter. Every site has their idiosyncrasies. Even DeviantArt has users jump through a few hoops to get the best version of an image.As an archive of sorts, it doesn't do well to upload inferior versions of images when better ones are readily available.Be careful when uploading from a mobile device, as they are too bandwidth-conscious and sometimes compress images when uploading even on wifi.Use direct-link uploading on your mobile device instead. https://dl.dropboxusercontent.com/u/61512916/Direct-Links.png
Be sure to also include the submission page as a link as well. Some websites' file names don't always provide an artist name, and it's nice to be able to quickly comment/fav/reblog on the original submission.The higher the resolution, the better. Watch out for upscale edits, though. Try to be sure the biggest version of an image you find is unaltered from how the artist uploaded it.PNG preferred over JPG. But don't go editing JPGs into PNGs. It has to have been saved as a PNG by the artist from the start. If you cannot notice the difference between a high-quality JPG and a PNG, then I envy you.With two JPGs identical in resolution and content, go with the one with a larger file size. A smaller file size means more compression was used, so there is likely to be a difference in compression artifacts.Google Reverse Image Search is a very useful tool for finding original submission pages if you cannot identify an artist. https://images.google.com/ (Click the camera in the search box.)
SauceNAO mostly indexes Pixiv, Nijie, Gelbooru, and other sites that mostly specialize in images by Japanese artists. http://saucenao.com/
You can find plugins to integrate these tools into your browser's context menu so they pop up when you right-click an image.FurAffinity does not allow hi-resolution images without circumvention. It resizes images larger than 1280px upon uploading and compresses them into medium-quality JPGs. If an artist's FA gallery is full of 1280px JPGs, try one of their galleries elsewhere.You can't always trust images on FA if they're a maximum of 1280px. FurAffinity sometimes hosts PNG images that are clearly JPGs. Pretty silly to see an image in a lossless format with compression artifacts. Look closely: https://dl.dropboxusercontent.com/u/61512916/1440607298.seisuke_nerv_bea_clothed_-_copy_CLOSEUP.pngTumblr's hi-resolution images go to a maximum width of 1280px or a maximum height of 1920px (whichever comes first). Again, see if they have an alternate gallery and compare resolutions and formats.Twitter uploads are often made from mobile devices that are bandwidth-conscious and compress images before sending them. Unless you're getting PNGs, use another gallery if possible.Pixiv, InkBunny, and Weasyl do not have a limit on resolution. They are generally preferred if an artist also posts there.Pinterest is just plain awful when it comes to image compression and crediting the artist. If you find something there you want to post, but cannot identify the artist, try using Google Reverse Image Search or SauceNAO to find an original submission page.Tumblr requires you to click around. Sometimes users save and upload the "_500" preview versions.
http://kikurages.tumblr.com/post/124070968394/
http://41.media.tumblr.com/e5bd8ab6e8f5f3e31b4ca3862c6ce678/tumblr_nrhg39BG781spud3zo1_500.jpg
http://41.media.tumblr.com/e5bd8ab6e8f5f3e31b4ca3862c6ce678/tumblr_nrhg39BG781spud3zo1_1280.jpgTwitter is not as obvious. Most users save and upload the smallest version, as presented in the Tweet itself. It requires a little URL trick to get the full image. Right-click an image and copy its URL (FireFox and Chrome). Open a new tab, paste in the URL and append ":orig" to the end of it and hit Enter.
https://twitter.com/bethesda/status/607640799702949888
https://pbs.twimg.com/media/CG7GFHAVAAE6Xas.png The image as it appears in the Tweet.
https://pbs.twimg.com/media/CG7GFHAVAAE6Xas.png:large "Large" size presented to the user when they click on the image in the Tweet.
https://pbs.twimg.com/media/CG7GFHAVAAE6Xas.png:orig The image's unaltered size. It might not always be larger than the ":large", but always try for the ":orig".With Pivix's dynamically-resizing "manga mode" for multi-page submissions, users must click the arrows in the corner to full-view the images before saving. Otherwise they save preview versions whereas the full image may be larger and/or in a lossless or less-compressed format.
https://e621.net/post/show/709622
Full image is higher resolution, and clicking the arrows also gives it to you as a lossless PNG:
http://www.pixiv.net/member_illust.php?mode=manga&illust_id=48584322
http://i3.pixiv.net/c/1200x1200/img-master/img/2015/02/06/11/01/23/48584322_p0_master1200.jpg
http://i3.pixiv.net/img-original/img/2015/02/06/11/01/23/48584322_p0.pngPixiv Ugoira animations are just archives of JPGs played in Javascript. Run a bookmark containing "javascript:window.location = pixiv.context.ugokuIllustFullscreenData.src;" (without quotation marks) while viewing a Pixiv Animation to download the archive. There is also an online converter at http://ugoira.dataprocessingclub.org/ that gives you the choice of both WebM or GIF. It is more recommended to use the online converter because it maintains the framerate of the original submission. Most animations benefit better with WebM than GIF because the frames are already compressed from the start (archive of JPGs).DeviantArt submissions:
http://pre12.deviantart.net/0b88/th/pre/i/2015/120/3/6/otachi_by_zaggatar-d8rmmk7.jpg Normal: As it appears when you arrive to the page.
http://img08.deviantart.net/d180/i/2015/120/3/6/otachi_by_zaggatar-d8rmmk7.jpg Large: Click the image.
https://e621.net/post/show/666443/ Full: Click the DOWNLOAD button, if applicable. (Depends on if the artist enables it, I think.)Avoid using 3rd-party sources like Twicsy because it only hosts the ":large" images and converts everything into JPGs. Twicsy is still a very useful tool because it presents Tweets in a nice gallery format instead of that ridiculous infinitely-scrolling format that Twitter feeds use, so be sure to click around for a link to the original Tweet and snag the ":orig" file instead of saving the image from Twicsy itself. http://twicsy.com/u/usernametl;dr, I care too much about image quality preservation and am posting this so I/we can link users to it as needed.