Adds a download button to the listmonk admin logs page to export the currently visible logs as a text file.

listmonk-logs-downloader.user.js

// ==UserScript==
// @name         listmonk – Logs Downloader
// @author       CodeAlDente (https://github.com/CodeAlDente)
// @namespace    https://gist.github.com/CodeAlDente/1e841d820284564f5b8e0f2482c612a7
// @version      1.0.0
// @description  Adds a native “Download logs” button to the listmonk admin logs page. When clicked, the visible logs are exported as a text file.
// @match        https://*/admin/settings/logs
// @run-at       document-idle
// @grant        none
// @license      MIT
// @homepageURL  https://gist.github.com/CodeAlDente/1e841d820284564f5b8e0f2482c612a7
// @supportURL   https://gist.github.com/CodeAlDente/1e841d820284564f5b8e0f2482c612a7
// ==/UserScript==

(function () {
    'use strict';

    // Extra guard in case the URL matching ever changes.
    // The script should never run outside the listmonk logs page.
    if (!location.pathname.startsWith('/admin/settings/logs')) {
        return;
    }

    // Formats a Date object into a filesystem-friendly timestamp
    // used for the exported log filename.
    function formatDate(date) {
        const pad = n => String(n).padStart(2, '0');
        return (
            date.getFullYear() + '-' +
            pad(date.getMonth() + 1) + '-' +
            pad(date.getDate()) + '_' +
            pad(date.getHours()) + '-' +
            pad(date.getMinutes()) + '-' +
            pad(date.getSeconds())
        );
    }

    // Reads the currently visible log lines from the DOM and
    // turns them into a plain text representation.
    function collectLogs() {
        const lines = document.querySelectorAll('.log-view .lines .line');
        if (!lines.length) {
            alert('No log lines found.');
            return '';
        }

        return Array.from(lines).map(line => {
            const ts = line.querySelector('.timestamp')?.innerText.replace(/\s+/g, ' ') ?? '';
            const file = line.querySelector('.file')?.innerText ?? '';
            const msg = line.querySelector('.log-message')?.innerText ?? '';
            return `${ts}${file}${msg}`.trim();
        }).join('\n');
    }

    // Creates a local text file and triggers a download in the browser.
    // Everything happens client-side; nothing is sent anywhere.
    function downloadLogs() {
        const text = collectLogs();
        if (!text) return;

        const now = new Date();
        const hostname = location.hostname.replace(/[^a-zA-Z0-9.-]/g, '_');
        const filename = `listmonk-logs_${hostname}_${formatDate(now)}.txt`;

        const blob = new Blob([text], { type: 'text/plain;charset=utf-8' });
        const url = URL.createObjectURL(blob);

        const a = document.createElement('a');
        a.href = url;
        a.download = filename;
        document.body.appendChild(a);
        a.click();

        URL.revokeObjectURL(url);
        a.remove();
    }

    // Injects the "Download logs" button into the listmonk UI.
    // Uses existing listmonk/Bulma button styles to blend in.
    function injectButton() {
        if (document.getElementById('listmonk-log-download-btn')) return;

        const logsSection = document.querySelector('section.logs');
        if (!logsSection) return;

        const title = logsSection.querySelector('h1.title');
        if (!title) return;

        const btn = document.createElement('button');
        btn.id = 'listmonk-log-download-btn';
        btn.type = 'button';
        btn.className = 'button is-primary';
        btn.style.marginBottom = '1rem';

        const span = document.createElement('span');
        span.textContent = 'Download logs';
        btn.appendChild(span);

        btn.addEventListener('click', downloadLogs);

        // Place the button directly below the page title,
        // matching the layout of other admin actions.
        title.insertAdjacentElement('afterend', btn);
    }

    // listmonk loads parts of the page dynamically.
    // This observer waits until the logs and title exist
    // before injecting the button.
    const observer = new MutationObserver(() => {
        if (
            document.querySelector('.log-view .lines .line') &&
            document.querySelector('section.logs h1.title')
        ) {
            injectButton();
        }
    });

    observer.observe(document.body, {
        childList: true,
        subtree: true
    });
})();

How to install

1. Install a userscript manager such as Tampermonkey in your browser.
2. Open the Gist and click Raw, then install the script when prompted.
3. Open the listmonk admin logs page (/admin/settings/logs) — the Download logs button will appear automatically.

Optional (recommended)
For extra safety, you can restrict the script to your own listmonk domain by editing the @match line in the script, or by adjusting the include/match settings in your userscript manager after installation.