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Blazer

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What Blazer is

Blazer is a free, open-source, self-hosted tool for exploring data with SQL and sharing charts and dashboards. It installs as a Ruby gem in a Rails application and can also run from a Docker image. Users can connect PostgreSQL, MySQL, Amazon Redshift, BigQuery, Snowflake, and SQL Server, then turn query columns into line, column, scatter, or pie charts. Dashboards combine several queries and show each result as a chart or table, while variables allow the same query to run with different values. Checks can detect bad data and email notifications when failures begin or recover; Slack delivery uses an incoming webhook. Blazer tracks queries, supports anomaly detection through Prophet, Trend, or AnomalyDetection.rb, and offers basic query permissions. CSV uploads can create tables, and cohort analysis is available with specified database requirements.

Who it suits

It suits teams comfortable with SQL, Rails, and self-hosting who need shared dashboards and data checks. It is also useful when query auditing and multiple database sources matter.

What it does well

Free and released under the MIT license
Supports several major data sources
Automatic charts from SQL results
Email and Slack check notifications
Tracks every query

What to know first

Requires self-hosting
Cohort analysis has database requirements
CSV uploads require PostgreSQL
Asynchronous queries require caching

Verdict

Blazer provides SQL-based exploration, dashboards, checks, and auditing in a self-hosted Rails setup. Its database requirements and caching model should be reviewed alongside authentication and read-only access recommendations.

Facts from Blazer's own pages

Anomaly detection: Blazer supports anomaly detection through Prophet, Trend, or AnomalyDetection.rb. · github.com, 12 Oct 2026
Charts: Blazer automatically generates charts from SQL result columns, including line, column, scatter, and pie charts. · github.com, 5 Oct 2026
Checks and alerts: Checks can send email alerts when bad data appears, and can also send notifications through a configured Slack incoming webhook. · github.com, 12 Oct 2026
CSV uploads: Blazer can create database tables from CSV uploads, and this feature requires PostgreSQL. · github.com, 12 Oct 2026
Dashboards: Dashboards can combine multiple queries, displaying charts when queries return chartable data and tables otherwise. · github.com, 12 Oct 2026
Database permissions: Blazer attempts to protect against modifying queries by running them in a transaction and rolling it back, and recommends a read-only database user as a safer approach. · github.com, 12 Oct 2026
Data sources: It supports multiple data sources, including PostgreSQL, MySQL, Redshift, BigQuery, Snowflake, and many others. · github.com, 12 Oct 2026
Deployment: Blazer is installed as a Ruby gem in a Rails application and is also available as a Docker image. · github.com, 12 Oct 2026
Hosting: Blazer is available as a Docker image and can be installed in a Rails application. · github.com, 5 Oct 2026
Installation: Blazer is installed as a Ruby gem in a Rails application and mounted as a dashboard route. · github.com, 5 Oct 2026
Integrations: Blazer can send check notifications to Slack through an incoming webhook. · github.com, 5 Oct 2026
Intended users: Blazer is presented for teams that want to explore data with SQL and share charts and dashboards. · github.com, 5 Oct 2026
License: The project is released under the MIT license. · github.com, 12 Oct 2026
Notable limits: Cohort analysis requires PostgreSQL or MySQL 8, and CSV uploads require PostgreSQL. · github.com, 5 Oct 2026
Performance: Queries run within a web request by default; asynchronous queries require caching, and multiple web processes require a centralized cache store. · github.com, 12 Oct 2026
Purpose: Blazer lets teams explore data with SQL, create charts and dashboards, and share them. · github.com, 12 Oct 2026
Query auditing: Blazer tracks all queries. · github.com, 5 Oct 2026
Query audits: Blazer tracks all queries. · github.com, 12 Oct 2026
Query permissions: Its basic permissions model can hide unnamed queries, limit queries beginning with # to their creator, and limit editing of queries beginning with * to their creator. · github.com, 12 Oct 2026
Security: Blazer can use an application's authentication system, and its documentation advises protecting the dashboard in production. · github.com, 12 Oct 2026
Variables: Queries can use variables so users can run the same query with different values. · github.com, 12 Oct 2026

Where Blazer stands on Freedom251

Business Intelligence Tools#31 of 89