The phrase "knows ins and outs" means to be intimately familiar with a topic or situation. There are several synonyms for this phrase that can be used in place of "knows ins and outs," including: 1. Knows the ropes 2. Familiar with the details 3. Well-versed 4. Experienced 5. Proficient 6. Skilled 7. Expert 8. Knowledgeable 9. Seasoned 10. Practiced By using these synonyms, you can add variety to your vocabulary and communicate your ideas in different ways, while still conveying the same meaning as "knows ins and outs".