Polygon.io is now Massive: what changed for developers

On October 30, 2025, Polygon.io renamed itself Massive. It is the same company with the same plans and prices, under new domains and new package names. A year on, the old endpoints still answer, but development has moved to the renamed SDKs. This is the migration checklist, checked against Massive's docs, its changelog and the package registries on 2026-10-29. MarketParquet is not affiliated with Massive.

Old name, new name

The Kotlin/JVM client is the exception: its main branch has moved to com.massive.client, but the last tagged release is still v5.1.2 (January 2024) under io.polygon.kotlin.sdk. Keep the old coordinates until a Massive-named release is tagged.

What did not change

• API keys. Existing keys work on both hosts.
• Plans and prices. massive.com/pricing matches the polygon.io page from October 2025.
• Flat-file credentials and layout. The bucket is still flatfiles, and S3 keys are still separate from the REST key (Dashboard, Keys). Massive calls flat files "unchanged". We could not test an old S3 key against the new host, so if a job fails there, regenerate the keys first.
• Data. Same feeds, same history, same response shapes.

From massive.com/pricing on 2026-10-29. Self-serve plans are for individual use, and Advanced requires non-professional status. Business ($2,499/mo) is the plan for firms.

The migration, in code

Python: swap the package and the import. The client calls are the same.

  pip uninstall polygon-api-client
  pip install massive

  # before
  from polygon import RESTClient
  # after
  from massive import RESTClient

  client = RESTClient()          # reads MASSIVE_API_KEY
  bars = client.get_aggs("AAPL", 1, "minute", "2025-11-03", "2025-11-03")

Rename the environment variable in every place it is set: shell profiles, CI secrets, Docker env files, systemd units. The massive client does not fall back to POLYGON_API_KEY, so a job that only sets the old name fails with an authentication error after the upgrade.

Raw HTTP and WebSocket clients: change the host only.

  https://api.polygon.io/v2/aggs/ticker/AAPL/range/1/day/2025-01-02/2025-01-31
  https://api.massive.com/v2/aggs/ticker/AAPL/range/1/day/2025-01-02/2025-01-31

  wss://socket.polygon.io/stocks   ->   wss://socket.massive.com/stocks

Flat files: point the S3 client at the new endpoint. The bucket name stays.

  aws s3 ls s3://flatfiles/us_stocks_sip/ \
      --endpoint-url https://files.massive.com

  # boto3
  s3 = boto3.client("s3", endpoint_url="https://files.massive.com",
                    aws_access_key_id=KEY, aws_secret_access_key=SECRET)

Search the codebase for the old names before you call it done: grep -rn "polygon.io\|POLYGON_API_KEY\|from polygon" . Then check firewall allow-lists and egress proxies. A rule that allows only *.polygon.io blocks the new hosts.

Is there a deadline?

None has been announced. The October 2025 announcement said old endpoints would be phased out after the transition, with notice. As of 2026-10-29, api.polygon.io still answers, and Massive's changelog (latest entry 2026-10-28) names no shutdown date. A "2026-11-01" cutoff circulates in some GitHub issues; it traces back to one project's own notes, not to Massive. The practical reason to migrate now is the SDKs: the polygon-named Python, JavaScript and Go packages get no new releases, and the old Python package pins certifi<2026.

Not the Polygon blockchain

Polygon.io was a market-data company. The Polygon network (MATIC, now POL) is an unrelated crypto project, and the shared name muddied search results for years. Massive did not give that as a reason for the rename, but the new name ends the mix-up.

If you only used it for historical data

Things worth knowing that the rename did not change. Flat files are gzipped CSV, one file per day per dataset. Each day's file is posted around 11 AM ET the next morning, and it is not adjusted for splits. REST aggregates are split-adjusted by default, and nothing is dividend-adjusted. History depth is set by the plan: five years on Starter, ten on Developer, and the full archive to September 2003 only on Advanced.

If what you need is years of split-adjusted bars in a backtest rather than a live feed, compare the costs in MarketParquet vs Massive. That page covers what Massive does that this archive does not: real-time data, options, trades and quotes.

FAQ

Do Polygon.io API keys still work? Yes, on both api.polygon.io and api.massive.com.

Is api.polygon.io shut down? Not as of 2026-10-29, and no date has been announced.

What is the new Python package? massive (from massive import RESTClient), Python 3.10 or newer, reading MASSIVE_API_KEY.

Did prices change? No. The plans, prices, limits and history depths are the same as before the rename.

Was Polygon.io acquired? No. It is a rename of the same company.

Related

MarketParquet vs Massive (formerly Polygon.io) · MarketParquet vs Databento · all guides

Checked 2026-10-29 against massive.com (blog, docs, pricing, changelog), PyPI, npm and the massive-com GitHub repositories. Confirm against Massive's own docs before changing production systems.