• Recommended image size: 1,200 x 628 pixels
• Image ratio: 1.9:1
• Text: 90 characters
• Headline: 25 characters
• Link description: 30 characters
• Only 20% of your ad can be covered in the text. 

Facebook's strict guidelines can cause an ad to have decreased reach potential or even be disapproved. To prevent this from happening, read these helpful tips: 

Tip 1: Do not use a creative that includes an excessive amount of text.
Tip 2: Include a 'Call to Action' Button. 
Tip 3: Your copy on the text, headline, and description should not be very lengthy. 
Tip 4: Create ads that appeal to your audience and relate to your offer.

Read more about Facebook Best Practices

• Best Practices for Text in Ads
• Best practices for making Ads more engaging 
• Best Practices for Image text