The European Union has a complex system of requirements for its passports. The requirements not only cover what must be present on the passport but also when a passport is actually needed. Each European Union member state used to have its own passport requirements but these are now being harmonized across the Union as a whole.
The Schengen Agreement
All European Union member states except the UK, Republic of Ireland, Bulgaria, Cyprus and Romania have eliminated border controls for travel inside Europe, meaning you do not need a passport to travel between “Schengen Area” countries. You still need passports to travel into Europe, or into the Schengen Area countries from outside, however. Similarly, a passport is required when leaving Europe, including within the Schengen Area.
All European passports have strict photograph requirements, due to the use of biometric data. These photos must be on a blank, cream or light grey background and must show the bearer's full face, without shadows or facial coverings. People may wear glasses in photographs only if their eyes are still visible in the picture (i.e. there is no glare or tinted glass).
Each European Union member state produces its own passports but they all bear certain similarities as part of the harmonization process. Covers must identify the document as a European Union passport, while the “Personal Details” page must list the bearer's name; date of birth; nationality; sex; and place of birth. All passports must present this information in English and French, although they may also bear the Member State's national language as well.
You will need a valid passport to travel in Europe but the term “valid” can be misleading. On top of covering you until the day you leave, the European Union requires three months of extra validity on the passports of non-EU citizens. This is to allow for potential delays and other setbacks. EU citizens do not require extra validity.
Some EU member states issue national identity cards to their citizens. These documents are accepted as valid forms of identification as a European Citizen, entitling the bearer to travel across European borders. When travelling in Europe, a valid ID card from a European member state is acceptable in place of a passport. A passport is still required for travel into and out of Europe.