JavaScript Navigator mimeTypes Property

What You’ll Learn

navigator.mimeTypes returns a MimeTypeArray of MIME types the browser reports. On modern engines that usually means hard-coded PDF types — or an empty list. Learn the MDN PDF check, description / suffixes, why pdfViewerEnabled is preferred, five examples, and try-it labs.

Introduction

Years ago, browsers exposed many plugin MIME types through navigator.mimeTypes (Flash, PDF plugins, and more). That made fingerprinting easy and was inconsistent.

Today the specification hard-codes the returned set. If the browser can display PDF files inline, you get application/pdf and text/pdf. Otherwise you get an empty list. MDN recommends using navigator.pdfViewerEnabled when you only need that PDF answer — do not infer it solely from mimeTypes in new code.

Understanding the mimeTypes Property

Think of it as a (now simplified) catalog of “file types this browser claims to handle via the legacy plugin model.”

• Value — a MimeTypeArray with length, item(index), and namedItem(name).
• Modern contents — PDF pair or empty (hard-coded).
• PDF entry fields — description "Portable Document Format", suffixes "pdf".
• Named access — navigator.mimeTypes["application/pdf"] or the in operator.
• Baseline — Widely available (MDN, since about July 2015).

📝 Syntax

General form of the property:

navigator.mimeTypes

Value

• A MimeTypeArray of MimeType objects (or empty when PDFs are not inline-viewable).

Common patterns

// MDN: test inline PDF via mimeTypes
if ("application/pdf" in navigator.mimeTypes) {
  const { description, suffixes } = navigator.mimeTypes["application/pdf"];
  console.log("Description: " + description + ", Suffix: " + suffixes);
}

// Preferred modern check for PDF viewing:
console.log("pdfViewerEnabled:", navigator.pdfViewerEnabled);

Examples Gallery

Examples follow MDN navigator.mimeTypes patterns. Prefer Try It Yourself — modern browsers often show two PDF entries or zero.

console.log("length: " + navigator.mimeTypes.length);
console.log("type: " + typeof navigator.mimeTypes);

length: 2
type: object
(or length: 0 when inline PDF is not available)

if ("application/pdf" in navigator.mimeTypes) {
  console.log("Inline PDF MIME types are listed");
} else {
  console.log("No application/pdf entry (empty list)");
}

Inline PDF MIME types are listed
(or: No application/pdf entry (empty list))

if ("application/pdf" in navigator.mimeTypes) {
  const { description, suffixes } = navigator.mimeTypes["application/pdf"];
  console.log("Description: " + description + ", Suffix: " + suffixes);
} else {
  console.log("PDF MimeType not listed");
}

Description: Portable Document Format, Suffix: pdf

const hasPdfMime = "application/pdf" in navigator.mimeTypes;
const pdfEnabled = Boolean(navigator.pdfViewerEnabled);
console.log("application/pdf in mimeTypes: " + hasPdfMime);
console.log("pdfViewerEnabled: " + pdfEnabled);
console.log(
  "Prefer pdfViewerEnabled for new PDF UI decisions"
);

application/pdf in mimeTypes: true
pdfViewerEnabled: true
Prefer pdfViewerEnabled for new PDF UI decisions

function mimeTypesSummary() {
  const list = navigator.mimeTypes;
  const hasPdf = "application/pdf" in list;
  const entry = hasPdf ? list["application/pdf"] : null;
  return {
    length: list.length,
    hasApplicationPdf: hasPdf,
    hasTextPdf: "text/pdf" in list,
    pdfViewerEnabled: Boolean(navigator.pdfViewerEnabled),
    description: entry ? entry.description : null,
    suffixes: entry ? entry.suffixes : null
  };
}

console.log(JSON.stringify(mimeTypesSummary(), null, 2));

{
  "length": 2,
  "hasApplicationPdf": true,
  "hasTextPdf": true,
  "pdfViewerEnabled": true,
  "description": "Portable Document Format",
  "suffixes": "pdf"
}

🚀 Common Use Cases

• Legacy PDF detection — understand older code that checks "application/pdf" in mimeTypes.
• Interview / learning — explain hard-coded PDF vs empty list behavior.
• Debug panels — show length and PDF MimeType fields beside pdfViewerEnabled.
• Migration — replace mimeTypes-based PDF checks with pdfViewerEnabled.
• History of plugins — contrast with old long plugin MIME lists (no longer exposed).

📝 Notes

• Baseline Widely available (MDN, since about July 2015).
• Not Deprecated, Experimental, or Non-standard on MDN’s property page — no status banner required.
• Modern list is hard-coded: PDF types or empty — not a full plugin inventory.
• Prefer navigator.pdfViewerEnabled for inline PDF feature detection.
• Related: mediaSession, mediaDevices, JavaScript hub.

💡 Best Practices