SEO firms typically measure success in terms of rankings, website traffic, lead generation, conversions, and brand recognition. They monitor the key performance indicators and analyze the results against the desired KPIs to find out if the campaign was successful and which areas need improvement. The SEO objectives are set before the campaign starts and the analytics tools measure the progress towards the set goals. SEO firms also identify opportunities for improvement, compare progress with the competition, and provide recommendations based on the data.