To verify the reliability of a free IELTS practice test, consider the following steps:

Source Reputation: Check if the practice test is provided by a reputable organization or website. Well-known educational institutions, official IELTS partners, and trusted educational resources are more likely to offer reliable materials.

Alignment with Official IELTS Format: Ensure that the practice test follows the official IELTS format. This includes the structure of the test, types of questions, timing, and scoring system. Reliable tests will closely mimic the actual test format.

Quality of Content: Evaluate the quality of the questions and passages. High-quality practice tests will have well-written questions that accurately reflect the difficulty level and subject matter of the official IELTS exam.