Espacenet patent database is a free online service for searching patents and patent applications. Espacenet was developed by the European Patent Office (EPO) in collaboration with the European Patent Organization’s member states. In 2015, the Espacenet worldwide service claimed to have records on more than 90 million patent publications.

Although, Espacenet patent database is one of the most used and recognized patent database around, it certainly has few limitations. Limitations of Espacenet are broadly classified under two categories: search limitations and results limitations.

The following search limitations apply in Espacenet:

• Maximum of ten search terms per field.
• Maximum of 20 search terms and 19 operators per mask.
• Left truncation not supported.
• Slashes can only be used for date entries and CPC /IPC symbol entries.
• Applicant /inventor names are not searchable in documents published in other character sets (Cyrillic, Greek, Japanese etc.).
• Diacritical characters (umlauts and accents) and slashes are not allowed when searching in the worldwide database.
• Stop words – common words such as FOR, WITH, THE, BUT, AND, OF, ANY, etc. – are not searchable as they would otherwise produce too many results.
• You cannot retrieve an XP document with the name of the author or limit a search to XP documents only.
• Some documents cannot be found using keywords as they do not have translated titles.

The following limitations apply to results in Espacenet:

• Maximum of 100,000 results per query but only the first 500 matching documents are listed.
• Maximum of 100 documents stored in My patents list for one year.
• You can save a maximum of 50 queries in the query history.
• The download function in ‘My patents’ list only works if the number of pages does not exceed 500 pages.
• The sort function is only available when the result list contains fewer than 500 hits.
• Lists can be only exported page by page (in other words, 30 documents in compact mode, 15 in extended mode).
• No statistical analysis is possible.