Adds Sci-Hub, LibGen, Anna's Archive, Sci-net, LibSTC Nexus, Spacefrontiers to Google Scholar results
// ==UserScript==
// @name Google Scholar to free PDFs
// @namespace ScholarToSciHub
// @version 1.20
// @description Adds Sci-Hub, LibGen, Anna's Archive, Sci-net, LibSTC Nexus, Spacefrontiers to Google Scholar results
// @author Bui Quoc Dung
// @match https://scholar.google.*/*
// @license AGPL-3.0-or-later
// @grant GM.xmlHttpRequest
// @connect *
// ==/UserScript==
const SCIHUB_URL = 'https://tesble.com/';
const LIBGEN_URL = 'https://libgen.li/';
const LIBGEN_SEARCH_URL = LIBGEN_URL + 'index.php?req=';
const ANNA_URL = 'https://annas-archive.org';
const ANNA_SCIDB_URL = ANNA_URL + '/scidb/';
const ANNA_CHECK_URL = ANNA_URL + '/search?index=journals&q=';
const LIBSTC_URL = 'https://hub.libstc.cc/';
const SCINET_URL = 'https://sci-net.xyz/';
const SPACEFRONTIERS_URL = 'https://spacefrontiers.org/';
const CROSSREF_URL = 'https://api.crossref.org/works?query.title=';
const DOI_REGEX = /\b(10\.\d{4,}(?:\.\d+)*\/(?:(?!["&'<>])\S)+)\b/gi;
function httpRequest(details) {
return new Promise((resolve, reject) => {
GM.xmlHttpRequest({
...details,
onload: resolve,
onerror: reject
});
});
}
function updateLink(span, text, href, isNo = false) {
const link = document.createElement('a');
link.href = href;
link.target = '_blank';
link.rel = 'noopener noreferrer';
link.style.fontSize = '15px';
if (isNo) link.style.color = 'gray';
link.innerHTML = text.replace('[PDF]', '<b>[PDF]</b>').replace('[Chat]', '<b>[Chat]</b>').replace('[Maybe]', '<b>[Maybe]</b>');
span.replaceWith(link);
}
function addLoadingIndicator(container) {
const span = document.createElement('div');
span.textContent = 'Loading...';
span.style.marginBottom = '4px';
span.style.color = 'gray';
span.style.fontSize = '15px';
container.appendChild(span);
return span;
}
async function fetchDOI(titleLink) {
try {
const res = await httpRequest({ method: 'GET', url: titleLink.href });
const match = res.responseText.match(DOI_REGEX);
if (match) return match[0].replace(/\/(full\/html|full|pdf|epdf|abs|abstract)$/i, '');
const title = encodeURIComponent(titleLink.textContent.trim());
const crRes = await httpRequest({ method: 'GET', url: `${CROSSREF_URL}${title}&rows=1` });
const data = JSON.parse(crRes.responseText);
return data.message.items?.[0]?.DOI || null;
} catch {
return null;
}
}
async function checkLibgen(title, doi, span) {
const trySearch = async (query) => {
try {
const res = await httpRequest({ method: 'GET', url: LIBGEN_SEARCH_URL + query });
const doc = new DOMParser().parseFromString(res.responseText, 'text/html');
const table = doc.querySelector('.table.table-striped');
const firstRow = table?.querySelector('tbody > tr');
const secondTd = firstRow?.querySelectorAll('td')?.[1];
const linkEl = secondTd?.querySelector('a[href^="edition.php?id="]');
if (linkEl) {
const href = linkEl.getAttribute('href');
const detailUrl = LIBGEN_URL + href;
const detailRes = await httpRequest({ method: 'GET', url: detailUrl });
const detailDoc = new DOMParser().parseFromString(detailRes.responseText, 'text/html');
const hasPDF = !!detailDoc.querySelector('table');
if (hasPDF) {
updateLink(span, '[PDF] LibGen', LIBGEN_SEARCH_URL + query);
return true;
}
}
} catch (e) {
console.error('LibGen check failed for query:', query, e);
}
return false;
};
const encTitle = encodeURIComponent(title);
if (!(await trySearch(encTitle)) && doi) {
const encDOI = encodeURIComponent(doi);
if (!(await trySearch(encDOI))) {
updateLink(span, '[No] LibGen', LIBGEN_SEARCH_URL + encDOI, true);
}
} else if (!doi) {
updateLink(span, '[No] LibGen', LIBGEN_SEARCH_URL + encTitle, true);
}
}
async function checkSciHub(href, doi, span) {
const tryURL = async (url) => {
try {
const res = await httpRequest({ method: 'GET', url });
if (/iframe|embed/.test(res.responseText)) {
updateLink(span, '[PDF] Sci-Hub', url);
return true;
}
} catch {}
return false;
};
if (!(await tryURL(SCIHUB_URL + href)) && doi) {
if (!(await tryURL(SCIHUB_URL + doi))) {
updateLink(span, '[No] Sci-Hub', SCIHUB_URL + doi, true);
}
} else if (!doi) updateLink(span, '[No] Sci-Hub', SCIHUB_URL + href, true);
}
async function checkAnna(doi, span, retry = 0) {
const checkUrl = ANNA_CHECK_URL + encodeURIComponent(doi);
const directUrl = ANNA_SCIDB_URL + doi;
try {
const res = await httpRequest({ method: 'GET', url: checkUrl });
const doc = new DOMParser().parseFromString(res.responseText, 'text/html');
const bodyText = doc.body.textContent;
if (bodyText.includes("Rate limited") && retry < 10) {
setTimeout(() => checkAnna(doi, span, retry + 1), 5000);
return;
}
const found = doc.querySelector('.mt-4.uppercase.text-xs.text-gray-500') ||
[...doc.querySelectorAll('div.text-gray-500')].some(div => div.textContent.includes(doi));
if (found) {
const res2 = await httpRequest({ method: 'GET', url: directUrl });
const doc2 = new DOMParser().parseFromString(res2.responseText, 'text/html');
const hasPDF = doc2.querySelector('.pdfViewer, #viewerContainer, iframe[src*="viewer.html?file="]');
updateLink(span, hasPDF ? '[PDF] Anna' : '[Maybe] Anna', directUrl);
} else {
updateLink(span, '[No] Anna', checkUrl, true);
}
} catch {
updateLink(span, '[No] Anna', checkUrl, true);
}
}
async function checkLibSTC(doi, span) {
try {
const res = await httpRequest({ method: 'HEAD', url: LIBSTC_URL + doi + '.pdf' });
const isPDF = res.status === 200 && res.responseHeaders.toLowerCase().includes('application/pdf');
updateLink(span, isPDF ? '[PDF] LibSTC' : '[No] LibSTC', LIBSTC_URL + doi + '.pdf', !isPDF);
} catch {
updateLink(span, '[No] LibSTC', LIBSTC_URL + doi + '.pdf', true);
}
}
async function checkSciNet(doi, span) {
try {
const res = await httpRequest({ method: 'GET', url: SCINET_URL + doi });
updateLink(span, /iframe|pdf|embed/.test(res.responseText) ? '[PDF] Sci-net' : '[No] Sci-net', SCINET_URL + doi, !/pdf/.test(res.responseText));
} catch {
updateLink(span, '[No] Sci-net', SCINET_URL + doi, true);
}
}
async function checkSpaceFrontiers(doi, span) {
const checkUrl = SPACEFRONTIERS_URL + 'r/' + doi;
const chatUrl = SPACEFRONTIERS_URL + 'c?context=' + encodeURIComponent(JSON.stringify({ uris: [`doi://${doi}`] })) + '&no-auto-search=1';
try {
const res = await httpRequest({ method: 'GET', url: checkUrl });
const doc = new DOMParser().parseFromString(res.responseText, 'text/html');
const hasChat = doc.querySelector('span.relative.flex')?.textContent.includes('Chat with the Research');
updateLink(span, hasChat ? '[Chat] Spacefrontiers' : '[No] Spacefrontiers', hasChat ? chatUrl : checkUrl, !hasChat);
} catch {
updateLink(span, '[No] Spacefrontiers', checkUrl, true);
}
}
async function processEntry(result) {
const titleLink = result.querySelector('.gs_rt a');
if (!titleLink) return;
let buttonContainer = result.querySelector('.gs_or_ggsm');
if (!buttonContainer) {
const div = document.createElement('div');
div.className = 'gs_ggs gs_fl';
div.innerHTML = '<div class="gs_ggsd"><div class="gs_or_ggsm"></div></div>';
result.insertBefore(div, result.firstChild);
buttonContainer = div.querySelector('.gs_or_ggsm');
}
if (buttonContainer.classList.contains('scihub-processed')) return;
buttonContainer.classList.add('scihub-processed');
const row1 = document.createElement('span');
row1.style.display = 'inline-flex'; row1.style.gap = '6px';
const scihubSpan = addLoadingIndicator(row1);
const libgenSpan = addLoadingIndicator(row1);
const row2 = document.createElement('span');
row2.style.display = 'inline-flex'; row2.style.gap = '6px';
const annaSpan = addLoadingIndicator(row2);
const scinetSpan = addLoadingIndicator(row2);
const row3 = document.createElement('span');
row3.style.display = 'flex'; row3.style.gap = '6px';
const libstcSpan = addLoadingIndicator(row3);
const row4 = document.createElement('span');
row4.style.display = 'flex'; row4.style.gap = '6px';
const spacefrontiersSpan = addLoadingIndicator(row4);
[row1, row2, row3, row4].forEach(r => buttonContainer.appendChild(r));
const doi = await fetchDOI(titleLink);
checkLibgen(titleLink.textContent, doi, libgenSpan);
checkSciHub(titleLink.href, doi, scihubSpan);
if (doi) {
checkAnna(doi, annaSpan);
checkSciNet(doi, scinetSpan);
checkLibSTC(doi, libstcSpan);
checkSpaceFrontiers(doi, spacefrontiersSpan);
} else {
[annaSpan, scinetSpan, libstcSpan, spacefrontiersSpan].forEach(span =>
updateLink(span, '[No] Source', '#', true));
}
}
async function addButtons() {
const results = document.querySelectorAll('#gs_res_ccl_mid .gs_r.gs_or.gs_scl');
for (const result of results) await processEntry(result);
}
addButtons();
new MutationObserver(() => addButtons()).observe(document.body, { childList: true, subtree: true });