List all available meta data keys in your vault, to i.e. check which ones are duplicated or unused.

List all meta data available in your vault

Basic

Keys in lower case and without spaces

Keys are listed in lower case here. Due to the fact that dataview saves a "sanitized" meta data key thats all lower-case, keys containing capitalized letters would be duplicated. So TotalPages will show up as totalpages. The same counts for keys that contains spaces: The sanitized version uses dashes instead, so go to sleep will show up as go-to-sleep

const metadata = [];

dv.pages().forEach(page => {
    Object.keys(page).forEach(key => {
        key = key.toLowerCase().replaceAll(" ", "-")
        if (key === 'file' || metadata.indexOf(key) >= 0) return;

        metadata.push(key)
    })
})

dv.list(metadata.sort())

Variants

Rendering a table with all meta data fields and the files they are contained in

Memory intensive calculation

Depending on the size of your vault and meta data usage, this query can cause your vault to freeze or crash. If you have a lot of data, better use the next variant that only shows up to 5 containing pages and is less straining on your computer.

Add dataviewjs to code block

This query is disabled by default, otherwise opening up this page would take quite some time. If you want to see the result - or use the query in your own vault, be sure to add a dataviewjs right on the first three backticks to enable it.

const metadataMap = {};

dv.pages().forEach(page => {
    Object.keys(page).forEach(metadata => {
        metadata = metadata.toLowerCase().replaceAll(" ", "-")
        if (metadata === 'file') return;
        if (!metadataMap[metadata]) {
            metadataMap[metadata] = []
        }
        if (!metadataMap[metadata].some(l => l.path === page.file.link.path)) {
            metadataMap[metadata].push(page.file.link);
        }
    })
})

dv.table(["meta data", "pages"], Object.keys(metadataMap).map(key => [key, metadataMap[key]]))

Rendering a table with all meta data fields and the first 5 files they are contained in

Memory intensive calculation

While this query is easier on your memory than the one listing all pages, it's still quite hungry. If the query does not render, try to reduce pagelimit to a smaller number.

const pagelimit = 5;
const metadataMap = {};

dv.pages().forEach(page => {
    Object.keys(page).forEach(metadata => {
        if (metadata === 'file') return;
        metadata = metadata.toLowerCase().replaceAll(" ", "-")
        if (!metadataMap[metadata]) {
            metadataMap[metadata] = []
        }
        if (!metadataMap[metadata].some(l => l.path === page.file.link.path)) {
            metadataMap[metadata].push(page.file.link);
        }
    })
})

dv.table(["meta data", "page count", `pages (first ${pagelimit})`], Object.keys(metadataMap).sort().map(key => [key, metadataMap[key].length, dv.array(metadataMap[key]).limit(pagelimit)]))