Dedupe a Google Sheet with Apps Script

Setup, once

1. Create a free API key at /app.
2. In your sheet: Extensions → Apps Script, paste the script below, save.
3. In the script editor: Project Settings → Script Properties, add DEDUPE_KEY with your key.
4. Reload the sheet. A Dedupe.dev menu appears.

The script

const FUZZY = false;      // true for fuzzy name matching
const THRESHOLD = 0.88;   // used only when FUZZY is true
const KEY_COLUMNS = [];   // zero-based, e.g. [0] for column A; [] = whole row

function onOpen() {
  SpreadsheetApp.getUi().createMenu("Dedupe.dev")
    .addItem("Remove duplicate rows", "dedupeActiveSheet")
    .addToUi();
}

function dedupeActiveSheet() {
  const sheet = SpreadsheetApp.getActiveSheet();
  const rows = sheet.getDataRange().getDisplayValues();
  const csv = rows.map(r => r.map(cell => {
    const s = String(cell);
    return /[",\n\r]/.test(s) ? '"' + s.replace(/"/g, '""') + '"' : s;
  }).join(",")).join("\n");

  const key = PropertiesService.getScriptProperties().getProperty("DEDUPE_KEY");
  const res = UrlFetchApp.fetch("https://dedupe.dev/api/dedupe", {
    method: "post",
    contentType: "application/json",
    headers: { Authorization: "Bearer " + key },
    payload: JSON.stringify({
      mode: "rows",
      data: csv,
      options: { keyColumns: KEY_COLUMNS, hasHeader: true,
                 fuzzy: FUZZY, threshold: FUZZY ? THRESHOLD : undefined },
    }),
    muteHttpExceptions: true,
  });
  const body = JSON.parse(res.getContentText());
  if (res.getResponseCode() !== 200) throw new Error(body.error);

  const cleaned = Utilities.parseCsv(body.result);
  sheet.clearContents();
  sheet.getRange(1, 1, cleaned.length, cleaned[0].length).setValues(cleaned);
  SpreadsheetApp.getActiveSpreadsheet().toast(
    body.kept + " rows kept, " + body.removed + " duplicates removed", "Dedupe.dev");
}

What to know before running it

The script replaces the sheet's contents with the deduplicated rows, so run it on a copy the first time. Rows travel to the API over HTTPS and are processed in memory, never stored; if the sheet must not leave your machine at all, use the browser tool on a CSV download instead, which is free and uploads nothing. Each run is metered like any API call (one unit per row), and appears in your dashboard with its row counts. To run it nightly with no clicks, add a time-driven trigger in the script editor pointing at dedupeActiveSheet.

Last updated July 27, 2026