|If you want to go to the tool directly, try the stable version (highly recommended). In addition, development versions are referenced below.|
SVG Check is a Toolserver tool designed to make the uploaders of file in the SVG (.svg) format a little easier. As it stands, MediaWiki converts files in the format into PNG (.png) files before display, for a number of reasons. This process produces a number of quirks and idiosyncrasies which have, in the past, required repeated uploading and general help to sort out.
SVG Check eases this process by allowing users to preview the eventual display of an SVG without going through the formality of uploading it, and without creating a permanent record of the potentially botched version. It can also be set to scan the file for errors, and present advice specific to that problem. If you want to contribute some new errors, you can leave a note on the talk page.
Known issues 
- Renderings are temporary; how temporary is presently decided on how close to the hour you uploaded it rather than a set time, which can be awkward (all versions).
- Some fonts render very slightly differently on SVG Check vs. MediaWiki (all versions).
- See also: Commons:Transition to SVG
Development versions 
At present, two versions of the tool are available: the stable version (highly recommended), and a bleeding-edge version, which includes some optimisation facilities. Future versions will come with a "fix this SVG" module.