about:blank file viewer. Copy-paste this into the console, then drop files into the page to view them.

audio_min.js

let d=document.body,n='\n',f=d.ondragover=e=>e.preventDefault();d.style.whiteSpace='pre';d.ondrop=e=>[f(e)].map.call(e.dataTransfer.files,f=>{e=new Audio(URL.createObjectURL(f));e.controls=e.loop=1;d.append(f.name+n,e,n+n)})

file_viewer.js

// file_viewer.js
// This is a simple file viewer that allows you to drag and drop files onto the page and view them.

Object.assign(document.body.style, {
    fontFamily: 'sans-serif',
    display: 'grid',
    gridTemplateColumns: 'repeat(auto-fill, minmax(300px, 1fr))',
    gridGap: '1em'
});
const fullScreenStyle = {
    position: 'fixed',
    objectFit: 'contain',
    background: '#fff',
    top: '0', left: '0', width: '100%', height: '100%', zIndex: '1000',
};
const regularStyle = {position: 'static', width: 'auto', height: 'auto'};
const fileView = function(name, element) {
    const el = document.createElement('div');
    const nameEl = document.createElement('div');
    nameEl.innerText = name;
    el.append(nameEl, element);
    return el;
}
const stopOthers = function() {
    Array.from(document.querySelectorAll('video, audio')).forEach(el => {
        if (el !== this) el.pause();
    });
};
const handleNextPlay = function() {
    const els = Array.from(document.querySelectorAll('video, audio'));
    const next = els[(els.indexOf(this) + 1) % els.length];
    next.currentTime = 0;
    if (document.fullscreenElement === this) {
        if (!this.origSrc) this.origSrc = this.src;
        // When we leave fullscreen, we need to reset the src to the origSrc.
        this.onfullscreenchange = () => {
            if (document.fullscreenElement !== this) this.src = this.origSrc;
        };
        this.src = next.src;
        this.play();
    } else {
        next.play();
    }
};
document.body.addEventListener("dragover", (ev) => ev.preventDefault());
document.body.addEventListener('drop', ev => {
    ev.preventDefault();
    Array.from(ev.dataTransfer.files).forEach(f => {
        let type = f.type.replace(/^image/, 'img').split("/")[0];
        if (!/^(video|audio|img)/.test(type)) type = 'iframe';
        let el = document.createElement(type);
        el.src = URL.createObjectURL(f);
        el.playsInline = true;
        el.controls = true;
        el.onplay = stopOthers;
        el.onended = handleNextPlay;
        el.style.maxWidth = '100%';
        if (type === 'iframe') {
            const iframe = el;
            Object.assign(iframe.style, {
                width: '100%',
                background: '#fff',
                border: '1px solid #eee',
            });
            const container = document.createElement('div');
            // Add a fullscreen button to the iframe.
            const fs = document.createElement('button');
            fs.innerText = 'Toggle Fullscreen';
            fs.onclick = () => {
                if (container.style.position === 'fixed') {
                    Object.assign(container.style, regularStyle);
                    Object.assign(iframe.style, {width: '100%', height: 'auto'});
                    return;
                }
                Object.assign(container.style, fullScreenStyle);
                Object.assign(iframe.style, {width: '100%', height: 'calc(100% - 2em)'});
            }
            container.append(iframe, fs);
            el = container;
        } else if (type === 'img') {
            el.onclick = () => {
                if (el.style.position === 'fixed') {
                    Object.assign(el.style, regularStyle);
                    return;
                }
                Object.assign(el.style, fullScreenStyle);
            };
        }
        document.body.append(fileView(f.name, el));
    });
});

multiview_min.js

let d=document,b=d.body,n='\n',c='create',f=b.ondragover=e=>e.preventDefault();b.style.whiteSpace='pre';b.ondrop=e=>[f(e)].map.call(e.dataTransfer.files,f=>{e=d[c+'Element'](f.type.split("/")[0].replace('image','img'));e.src=URL[c+'ObjectURL'](f);e.style.width='25%';e.controls=e.loop=1;b.append(f.name+n,e,n+n)})