There are many free platforms for patent retrieval, including China National Intellectual Property Administration (not recommended, usually very slow) or the Patent Information Center of Intellectual Property Publishing House, all of which are official. The others are sooPAT or Baiteng. Com (Baidu can find it in one click) is a free search platform with complete information, so don't worry about the authenticity or authority of the information.
In addition, patent search can be in-depth or simple. If it is simple, you can search by yourself with several keywords. If you want to do it in depth, it is recommended to entrust an experienced intellectual property consulting company or agency to make the search more comprehensive.
Because the purpose of patent retrieval is to avoid potential infringement risks in the future, the retrieval strategy is different from novelty retrieval in the dimension of screening retrieved patents, and it is to screen and compare patents from the perspective of infringement judgment.
Comparing the retrieved patents from the perspective of infringement judgment belongs to the work of patent early warning, and there are many professional knowledge involved in infringement judgment, so it is better for experienced intellectual property consulting companies or agencies to do it.