Keep these limitations in mind when working with rich text area fields.
Available in: Salesforce Classic
Available in: Contact Manager, Group, Professional, Enterprise, Performance, Unlimited, Developer, and Database.com Editions
Salesforce supports up to 131,072 characters for each rich text area field, including the HTML tags. If desired, you can set a lower limit.
An object can contain unlimited rich text area and long text area fields, although your edition’s limit for total custom fields allowed on an object, regardless of field type, applies. Each object can contain 1,600,000 characters across long text area and rich text area fields. When you create a long text area or rich text area field, you set a character limit for the field—the maximum length of the text that can be entered. The default character limit for long text area and rich text area fields is 32,768 (32 KB). The maximum character limit for long text area and rich text area fields is 131,072 (128 KB). The minimum character limit is 256.
You can’t paste special characters, such as bullets or curly quotes, into a rich text field from another application. It’s best to type or paste in plain text and use the rich text editor to format it.
You can’t disable specific rich text area features. For example, you can't disable support for hyperlinks or images on certain fields.