So what makes Bitrix24 best online CRM with API access? First, all records in cloud are free and unlimited without any charges for API access. Second, Bitrix24 comes with an extremely powerful business process and marketing automation features. Third, Bitrix24 comes with built-in free telephony platform that is on par even with the most powerful options on the market. Forth, you get quotes, invoices, tasks, email marketing, projects and document management options. Finally, experienced Bitrix24 partners are available for hire should you need any assistance with API consultations.
Bitrix24 CRM manual is available here.
If you are interested in buying self-hosted editions of Bitrix24, which come with API, CMS and source code, can be easily customized and integrated with other tools, please download a trial version here.