Every ERPNext rollout has a corner of the business still run out of Google Sheets — a sales pipeline the reps actually update, a supplier price list finance maintains, a field-ops tracker, a marketing lead sheet. The data has to reach ERPNext, so someone exports CSVs and babysits the Data Import Tool a few times a week, or copies rows by hand. ERPNext core gives you a one-shot Data Import and a manual "Export" button, but no scheduled, incremental, bidirectional link to a live spreadsheet. There is no native cron that says "every hour, pull new rows from this worksheet into Lead, updating anything that already exists." That gap is exactly where this app lives.

We build a proper Frappe app — its own module, DocTypes, and hooks.py wiring — installed on your ERPNext site. A Sheet Sync Profile DocType defines each connection: the Google spreadsheet ID and worksheet, the target ERPNext DocType, the field-to-column mapping, the sync mode, and the schedule. Authentication is a Google service account whose JSON key is stored server-side (never in the browser), so the sheet is shared to the service account email and no per-user OAuth dance is required. Column-to-field mapping is configured through a child table in the UI — no code editing to add or remap a field — and each mapping can carry a light transform (date parsing, number coercion, Link-field resolution by name) so a messy spreadsheet lands as clean ERPNext data.

Technically, the engine runs on Frappe's scheduler. You choose hourly, daily, or a specific cron expression, registered under scheduler_events in hooks.py, and the job runs in the background worker — not the web request — so large sheets never time out. Insert mode appends new rows; upsert mode uses a key column you nominate (e.g. an email, an item code, an external ID) to update the matching ERPNext document or create it if absent, via frappe.get_doc / db lookups with permission checks intact. Incremental sync tracks a per-profile watermark (last-synced row or a timestamp column) so each run only processes what changed instead of re-importing the whole sheet. Every run writes a Sheet Sync Log row — counts of inserted, updated, skipped, and errored records, with per-row error detail — so you can see exactly what happened and re-run a failed batch. The optional two-way write-back is driven by ERPNext doc_events (on_update, after_insert) hooks that push the changed document back to the mapped worksheet through the Google Sheets API, with loop-prevention so a sync-in doesn't trigger a sync-out ping-pong. Whitelisted methods expose a manual "Sync now" button and can be called from the Frappe REST API for on-demand runs.

Because this is build-to-order, nothing is a mystery download. We start with a short scoping call to confirm your DocTypes, the worksheets, the key columns for upsert, and whether you need write-back. We build against Frappe/ERPNext v15 or v16, validate on a staging copy of your site with your real sheets during UAT, then install on production with a rollback plan. You receive the full app source in a git repository you own, along with install and configuration docs, a user guide, a training session, and a post-go-live support window. Typical delivery is one working week from confirmed scope, depending on how many DocTypes and transforms are in play.