For an online business, a detailed and in depth business plan is usually not necessary unless you are trying to combine your online business with a traditional business. For most online business startups, the detail involved with planning a traditional business is not required. However, it would still be beneficial to you if most of the topics were still covered, even if only briefly. Having a written plan in front of you will help you to focus on important aspects of the business.
Some people think that they do not need a business plan for a small business. But let me make it clear that the size of the business doesn't matter. Whether small or big, you need a plan. If you need a plan as an individual and for your family, then why not have a plan for your small business? Like for individuals and families, you need to plan for your online small business. A business plan shows you what you would like to achieve and how to achieve it. Although not all plans are written down, a good business plan should be written down. If you have it in your head, it's high time you spent some time to write it down for better results.