Overview

Error 100339 is a feed processing error that Amazon triggers when it detects HTML tags, JavaScript, CSS, or other code markup embedded within your product listing attributes. This is a common issue that can prevent your listings from going live or updating properly, and it frequently catches sellers off guard — especially those who copy and paste content from websites or word processors into their product detail fields.

Key Points / What Sellers Need to Know

• Plain text only — Amazon requires all product detail page content to be submitted in plain text format, with no HTML, JavaScript, CSS, or any other type of code markup.
• Common culprits — HTML tags like <p>, <br>, <b>, <i>, and <strong> are the most frequent triggers for this error, often introduced through copy-paste workflows.
• Affects multiple fields — The error can be triggered by code found in titles, bullet points, descriptions, generic keywords, or any other product attribute field.
• Hidden formatting is a risk — Even if you didn't intentionally add code, pasting content from a website, email client, or rich text editor can silently introduce markup that triggers this error.
• Check your feed report — Amazon's feed processing summary report will identify the specific attribute that contains the offending markup, helping you pinpoint exactly where to make corrections.

Why This Error Occurs

Amazon enforces strict content formatting standards across its product catalog to ensure a consistent shopping experience. When sellers submit product data through feeds — whether via flat files, the API, or third-party tools — Amazon's systems scan every attribute field for non-compliant content. Error 100339 fires when the system detects anything that resembles code rather than plain product information. This includes obvious HTML tags, but also less apparent issues like special Unicode characters, CSS styling fragments, or JavaScript snippets that may have been inadvertently embedded. Sellers who manage large catalogs or use content management systems to generate their listings are particularly susceptible, since automated workflows can introduce formatting artifacts that are invisible in a standard text editor but clearly detectable by Amazon's validation engine.