Höttl was born in Vienna, Austria-Hungary, 19 March 1915. In 1938, at the age of only 23, he received a doctorate in history from the University of Vienna. While still a student there, he joined the Nazi Party (member no. 6309616) and the SS (member no. 309510). From late 1939 until the end of the war in Europe, Höttl was employed almost without interruption by Germany's central intelligence and security agency, the Reichssicherheitshauptamt (RSHA) or Reich Main Security Office. The RSHA was made up of seven main departments, including: the Sicherheitsdienst (SD) or Security Service; the Sicherheitspolizei (SiPo) or Security Police, composed of the Gestapo (Secret State Police) and the Kriminalpolizei (Kripo) or Criminal Police.
Höttl was first stationed in Vienna with the SD foreign bureau and then moved to Berlin where he was promoted to the rank of SS-Sturmbannführer (major). In 1944 Höttl became the Ausland-SD's acting head of Intelligence and Counter Espionage in Central and South-East Europe. In March he was assigned to Budapest, where he served as second in command to Reichsführer-SS Heinrich Himmler's SS representative in Hungary. In addition, Höttl served as political advisor to Hitler's ambassador there, Edmund Veesenmayer, who reported to Berlin, for example, on the large-scale deportations in 1944 of Jews from Hungary.
Höttl died 27 June 1999 in Altaussee, Austria, aged 84.
After the war, Höttl figured prominently as a prosecution witness at the Nuremberg Trials. In an affidavit dated 25 November 1945, the thirty-year old Höttl described a conversation he held with Adolf Eichmann in August 1944 during the closing months of the war. The meeting of the two men took place at Höttl's office in Budapest:
"Approximately 4,000,000 Jews had been killed in the various concentration camps, while an additional 2,000,000 met death in other ways, the major part of whom were shot by operational squads of the Security Police during the campaign against Russia." 
- McNab, Chris. The SS: 1923–1945, p 41.
- Lumsden, Robin. A Collector's Guide To: The Allgemeine - SS, p 83.
- Nuremberg Trial proceedings, Vol. 3
- Höttl, Wilhelm. The Secret Front, Enigma Books, 1954, ISBN 1-929631-07-3
- The Trial of Adolf Eichmann, Vol 4, Session, 88. 
- Kahn, David. The Secret History of the Author of the Secret Front, Online publication.
- Lumsden, Robin (2002). A Collector's Guide to: The Allgemeine – SS. Ian Allan Publishing, Inc. ISBN 0-7110-2905-9.
- McNab, Chris (2009). The SS: 1923–1945. Amber Books Ltd. ISBN 978-1-906626-49-5.