How do I delete thousands of .jpg files, each a duplicate of a .heic file? I was shooting photos/videos with an iPhone 8 and syncing using macOS iTunes &amp; Photos on High Sierra.

For a period of two years, I have somehow ended up with a duplicate of every photo—several thousand duplicates.

Each duplicated photo is in two file types, one is in .HEIC and the other is in .JPG.

Each video from the same period has only one copy, in .MOV format.

I am assuming that it is prudent to delete the .jpg files and keep the .heic ones, since the latter can store live photos and since I can generate .jpg from them if needed.

How do I delete thousands of .jpg files, each a duplicate of a .heic file? The duplication started after I moved to Photos from iPhotos. A script that does the job with no confirmation is fine (I'd test it on one day).
One option is to use an AppleScript (or JavaScript for Automation, rather) such as the one I posted about here. I've copied its contents below*, and I've tried to include a fair amount of instructions between the post and comments in the code.
#!/usr/bin/osascript -l JavaScript
// findJpgHeicDuplicates.js
// https://n8henrie.com/2021/02/remove-duplicate-jpg-or-heic-photos-from-macos-photosapp/
//
// Quickstart:
//   - Copy this into a file, e.g. `findJpgHeicDuplicates.js`
//      - Alternatively, check the post above for a download link
//   - Make executable: `chmod +x findJpgHeicDuplicates.js`
//   - Modify the configuration in the `CUSTOMIZE` section if desired
//     - This is where you can configure getting rid of `.jpg` vs `.heic`
//   - Select a set of photos in Photos.app
//   - Run `./findJpgHeicDuplicates.js`
//   - Process the suspected duplicates in `Duplicates/timestamp`
//
//  Alternatively, users not comfortable with the command line can:
//    - open `Script Editor.app` on their Mac
//      - `/System/Applications/Utilities/Script Editor.app` on Big Sur
//    - create a new script
//    - Change the language to JavaScript (if `AppleScript` is displayed near
//      the top left)
//    - Copy and paste the contents of this script
//    - You will need to compile with `command` + `k` (or the hammer button) in
//      between each run or else you will get `Error: SyntaxError: Can't create
//      duplicate variable:`
//
// Apple's newish `.heic` image format compresses photos somewhat smaller than
// jpg with some loss of minor details. Unfortunately, many users like myself
// end up with numerous duplicate photos as a result -- half .jpg and half
// .heic -- which nullifies the space savings.
//
// This script uses filename (sans extension), the photo's timestamp*, and
// configurable fields in `criteria` (found in the `CUSTOMIZE` section) to find
// likely .heic/.jpg duplicates from a selected set of photos in MacOS
// Photos.app. If it finds a likely duplicate with at least one copy of the
// desired extension, it then moves all copies of the UNdesired filetype to an
// album named by the unix timestamp at the time of running within a folder
// named `Duplicates`. These can then be inspected, and if desired batch
// deleted with `command` + `delete`.
//
// * +/- 10 seconds, since most of my `.heic` files are timestamped ~1 second
//   after the `.jpg`
//
// Note that if adding many photos to an album at once, Photos.app may prompt
// for confirmation before doing so. Therefore, if you leave this script
// running and aren't there to accept the confirmation prompt, the script may
// time out while waiting for a response. Additionally, if your Mac sleeps
// while this is running, it may not work properly -- I recommend running
// `caffeinate -d` from the command prompt or using an application like
// `Caffeine` to disable sleep if you're going to run it while AFK. Thankfully,
// it seems that as long as you confirm the action it will often still work.
//
// I don't write much JavaScript, but I much prefer it to AppleScript. This
// should be non-destructive, but use it at your own risk. Make sure you have
// tested and working backups.
//
// Runs in about 19 minutes for my library of 20,233 pictures on my 2014 MBA.
//
// Tested on MacOS 11.1, Photos 6.0

'use strict'

// CUSTOMIZE
let getRidOfExtension = &quot;jpg&quot; // Only get rid of photos with this extension
let dupFolderName = &quot;Duplicates&quot;
let logInterval = 1000

let criteria = [
    // &quot;favorite&quot;,
    &quot;width&quot;,
    // &quot;pcls&quot;, // not sure what this is
    // &quot;size&quot;, // not recommended -- heic and jpg will have different sizes
    // &quot;location&quot;, // [123.456, -78.9]
    // &quot;keywords&quot;,
    &quot;height&quot;,
    // &quot;description&quot;,
    // &quot;altitude&quot;,
    // &quot;name&quot;, // often not set, not the same as filename
]
// END CUSTOMIZE

function getDetails(photo) {
    let properties = photo.properties()

    var details = {
        &quot;extension&quot;: properties[&quot;filename&quot;].toLowerCase().split(&quot;.&quot;).slice(-1)[0],
        &quot;timestamp&quot;: properties[&quot;date&quot;].getTime() / 1000, // in seconds
    }

    for (let criterion of criteria) {
        details[criterion] = properties[criterion]
    }
    return details
}

function run(argv) {
    let tsForAlbum = Date.now().toString()

    const photos = Application('Photos')
    let selection = photos.selection()
    let selectionLength = selection.length
    if (selectionLength &lt; 2) {
        throw new Error(&quot;Not enough photos selected&quot;)
    }

    let getRidOfExtensionLower = getRidOfExtension.toLowerCase()
    // { filename-sans-extension: [ {'selectionIdx': idx1, 'timestamp': ts, &quot;extension&quot;: ext } ] }
    var photomap = {}
    var duplicates = []
    for (let selectionIdx in selection) {
        if (selectionIdx % logInterval == 0) {
            console.log(&quot;Processing &quot; + selectionIdx + &quot; of &quot; + selectionLength)
        }
        let photo = selection[selectionIdx]

        // This script only intended for jpg and heic
        let filename = photo.filename()
        let lowername = filename.toLowerCase()
        if (!(lowername.endsWith(&quot;.jpg&quot;) || lowername.endsWith(&quot;.heic&quot;))) {
            continue
        }

        var details = getDetails(photo)
        details['selectionIdx'] = selectionIdx

        let stem = filename.replace(/(\.JPG$)|(\.HEIC$)/i, &quot;&quot;)
        if (!(stem in photomap)) {
            photomap[stem] = [details]
            continue
        }

        photomap[stem].push(details)
        let sameStem = photomap[stem]

        // filter for timestamps within 10 seconds of the current photo
        let timestamp = details['timestamp']
        let similarTimes = sameStem.filter(otherDetails =&gt; {
            let ts = otherDetails['timestamp']
            if (Math.abs(timestamp - ts) &lt; 10) {
                return true
            }
            return false
        })
        let detailsMatch = similarTimes.filter(otherDetails =&gt; {
            let keys = Object
                .keys(otherDetails)
                .filter(key =&gt; !([&quot;timestamp&quot;, &quot;extension&quot;, &quot;selectionIdx&quot;].includes(key)))
            for (let key of keys) {
                if (details[key] != otherDetails[key]) {
                    return false
                }
            }
            return true
        })

        // If filtering heic / jpg duplicates, we want to make sure there is at
        // least one of each filetype before we decide to filter the other out,
        // otherwise we might e.g. end up filtering both copies of duplicate
        // [jpg, jpg] (if configured to keep heic). Because this script only
        // puts *one* copy into the duplicates folder, which facilitates mass
        // deletion, this otherwise could end up causing unexpected data loss
        // if users aren't paying attention.
        let keepPhotos = detailsMatch.filter(each =&gt; each[&quot;extension&quot;] != getRidOfExtensionLower)
        if (keepPhotos.length &lt; 1) {
            continue
        }

        // Should always match itself
        if (detailsMatch.length &gt; 1) {
            (
                detailsMatch
                    .filter(details =&gt; details['extension'] == getRidOfExtensionLower)
                    .map(details =&gt; {
                        let sidx = details['selectionIdx']
                        duplicates.push(selection[sidx])
                })
            )
        }
    }

    console.log(&quot;Found &quot; + duplicates.length + &quot; suspected duplicate[s]&quot;)
    if (duplicates.length == 0) {
        return
    }

    let duplicatesFolder = photos.folders.byName(dupFolderName)
    if (!duplicatesFolder.exists()) {
        photos.make({new: &quot;folder&quot;, named: dupFolderName})
    }
    let album = duplicatesFolder.albums.byName(tsForAlbum)
    if (!album.exists()) {
        photos.make({new: &quot;album&quot;, named: tsForAlbum, at: duplicatesFolder})
    }
    photos.add(duplicates, {to: album})
    console.log(&quot;Duplicates added to &quot; + dupFolderName + &quot;/&quot; + tsForAlbum)
}