Accurate hiking maps of Austria

In my opinion the best map is produced by the Federal Office of Metrology and Surveying (BEV - Bundesamt für Eich und vermessungswesen). They produce the so called OeK50 and OeK25 (austrian map - Oestereichische Karte in scale 1:50000 or 1:25000).

Unfortunately the print version can be rather expensive at 7EUR per part, but if you know which ones you need it is ok.

The online version is free, and they have an online shop. I think the Alpenverein mentioned before sells this map as well.

http://www.austrianmap.at/amap/index.php?SKN=1&XPX=637&YPX=492

Kompass are great: http://www.kompass.de/touren-und-regionen/touren/

Switch layer to Summer/Winter in top right to see the details like marked trails and contours (otherwise it shows Open Street Map with less details). There are even winter ski tours there.

I can recommend https://www.alpenvereinaktiv.com/ There is also an app for that - for free: https://www.alpenvereinaktiv.com/de/mobile-app.html

With the exception of the excellent BEV maps and their mediocre web-interface, all the previous answers are maps based on OpenStreetMap. Therefore, they are unlikely to differ in accuracy/level of detail. In my opinion OpenTopoMap is the best OSM-based map, as it has a clean interface without distractions and includes elevation-information.