There are various digital Tibetan dictionaries – many of them online, some also for installation:

Online Dictionaries

• Tibetan-English Dictionary application programmed by me (includes several dictionaries, like the 2015 version Jeffrey Hopkins’ dictionary, Rangjung Yeshe, the dung dkar mtshig mdzod chen mo and others)
• Dictionary of the Tibetan and Himalayan Library (includes several dictionaries, like Rangjung Yeshe and bod rgya mtshig mdzod chen mo)
• Tibetan Translation Tool – online version (includes several dictionaries, like Rangjung Yeshe and the 1992 version of Jeffrey Hopkins’ dictionary)
• Rangjung Yeshe Wiki (this website contains the entire Rangjung Yeshe dictionary. In addition contains many other entries about dharma-related topics which are constantly being extended. Therefore it is both – a Tibetan-English dictionary and an encyclopedia on various topics of Tibetan Buddhism.)
• Rigpa Wiki (This is a mix between a Tibetan-English dictionary and an English encyclopedia on various topics of Tibetan Buddhism)
• Kata Tibetan-English Dictionary (A community-created dictionary. Can be searched both in Tibetan and English)
• Online-version of the Illuminator Dictionary (this Tibetan dictionary by Tony Duff and others requires a yearly subscription but the dictionary is well worth it; an installable version is also available – see below)
• Nitarta Dictionary (this dictionary contains the Rangjung Yeshe dictionary and the bod rgya mtshig mdzod chen mo)

Installable Dictionaries and Dictionary Apps

• Tibetan-English Dictionary by Christian Steinert (android app) (includes several dictionaries, like the 2015 version Jeffrey Hopkins’ dictionary, the bod rgya mtshig mdzod chen mo and others. At present there is no iOS version of this app. However, the online web version of the app works well on small displays and can be used with iPhones and iPads while an internet connection is available)
• Tibetan Translation Tool – installation guide for offline version (includes several dictionaries, like Rangjung Yeshe and the 1992 version of Jeffrey Hopkins’ dictionary)
• Offline-version of the Illuminator Dictionary and other dictionaries (the Padmakara translation commitee offers various dictionary programs, like Tony Duff’s Tibetan-English dictionary, a revised digital version of the Chandra Das Tibetan-English dictionary, or a revised digital version of the bod rgya mtshig mdzod chen mo. The dictionaries are for sale but are well worth the price. The Illuminator Dictionary and various other dictionaries  are also available as iPhone/iPad apps in the Apple store. The apps are not currently available for Android)
• Lobsang Monlam Dictionary (This free dictionary program contains Tibetan-English entries and Tibetan-Tibetan entries from various sources.  An App version of this for android devices is also available in the Google play store; and an iOS version of the App is available in the Apple store)
• Golden Dict – (Golden Dict is a general dictionary program that can be used with many different dictionary databases – not only limited to Tibetan. On the linked page, a download version of the Rangjung Yeshe Tibetan-English dictionary for offline use is given. In addition it is possible to use the online versions of Rangjung Yeshe Wiki and Rigpa Wiki. The Program is available for Windows, MacOS, and Android)

Downloadable Dictionaries in PDF Format

• Tibetan-Sanskrit-English Dictionary UMA Institute for Tibetan Studies (this is the 2015 version of the dictionary by Jeffrey Hopkins and others)
• Tibetan-English-Tibetan Dictionary (contemporary dictionary by Huadan Zhaxi, Kevin Stuart, Rinchen Dorji, Gesang Norbu, Dorji Zhaxi, Rinchen Khar, Gongbu Caireng, and Sandra Benson)
• Tibetan-English dictionary with special reference to the prevailing dialects, H. A. Jäshke
• Tibetan and English dictionary by Alexander Csoma de Kőrös (Free on Google Books)
• A Tibetan-English dictionary with Sanskrit synonyms, Sarat Chandra Das
• Chinese-Tibetan-English Dictionary of New Daily Vocabulary
• An English-Tibetan dictionary, Zla-ba-Bsam-grub, Kazi
• English-Tibetan colloquial dictionary, Sir Charles Alfred Bell
• English-Tibetan Dictionary of Modern Tibetan – by Melvyn C. Goldstein (a digital copy can be borrowed temporarily)
• New Tibetan English Dictionary Of Modern Tibetan New Tibetan English Dictionary Of Modern Tibetan  – by Melvyn C. Goldstein