The first-to-file trademark rule is applied in the majority of the world. The countries that use the system are:
Algeria, Anguilla, Argentina, Austria, Belarus, Belize, Benelux, Bolivia, Botswana, Brazil, Chile, China, Colombia, Croatia, Curacao, Czech Republic, Dominican Republic, Ecuador, El Salvador, Estonia, European Union, Finland, France, Germany, Greece, Guatemala, Hungary, Iran, Japan, Jordan, Kazakhstan, Kuwait, Kyrgyzstan, Lithuania, Mexico, Moldova, Montenegro, Nicaragua, Nigeria, Norway, Peru, Philippines, Poland, Qatar, Romania, Russian Federation, Slovenia, South Korea, Spain, Syria, Taiwan, Uganda, Ukraine, United Kingdom, Venezuela, Vietnam, and Zambia.
In simple terms, in a first-to-file trademark system, it's important to apply for a trademark as soon as possible. In this system, the filing date gives the brand owner priority over anyone who either files an identical/confusingly similar application after them or uses the brand in commerce without an actual trademark registration.