Backed by mandō

One stream in.
Every destination served.

FanOut is the mission-critical data fan-out infrastructure that reads from any input stream and simultaneously writes to stdout and every file you need. Zero data loss. Zero compromise. Infinite surface area.

Start Free Trial See It In Action
4.2B+ Streams processed
99.99% Uptime SLA
< 1ms Fan-out latency

Trusted by pipeline-first teams at

Core Capabilities

Everything you need to fan out data at scale

FanOut reads from standard input and writes simultaneously to standard output and every destination file. One pipeline entry point. Unlimited egress. Ship faster.

⇉

Multi-Destination Write Engine

Copy standard input to each destination file AND to standard output simultaneously. One ingestion, infinite fan-out. This is the core primitive every data team has been missing.

⊕

Append Mode -a

Append to given files rather than overwriting. Protect existing data while continuously enriching destination logs. The compound interest of pipeline output — every run adds value without destroying what came before.

🛡️

Interrupt Shield -i

Ignore interrupt signals during critical fan-out operations. When your pipeline is mid-flight, FanOut ensures delivery continuity. SIGINT? Not on our watch. This is what "production-grade" actually means.

🔍

Pipe Diagnostics -p

Operate in a more appropriate mode with pipes. Full diagnostic output for write errors on non-pipe destinations. When something breaks, you know exactly what and where. Observability built into the core protocol.

⚙️

Output Error Policy Engine --output-error

Granular write-error behavior: warn, warn-nopipe, exit, or exit-nopipe. Configure exactly how your pipeline responds to destination failures. Four modes. Total control. Enterprise-grade resilience policies for every scenario.

∞

Unlimited Destinations

Pass as many file destinations as your infrastructure demands. There's no artificial cap. One stream fans out to 2 files, 20 files, 200 files. Horizontal scale for your data egress layer.

Architecture

How FanOut Works

A distributed fan-out topology in four primitive operations.

01

Ingest from stdin

FanOut opens a read channel on standard input. Any upstream data producer — log aggregators, ETL jobs, sensor feeds — writes into the pipeline. Single entry point. Zero configuration.

02

Fork the data path

Every byte is simultaneously routed to stdout (your primary consumer) and every registered destination file. The fork happens at the byte level — no buffering delays, no eventual consistency. Strong consistency guarantees from the ground up.

03

Apply write policies

Each destination is governed by your configured error policy. Warn, exit, or selectively skip broken pipes. FanOut's Output Error Policy Engine ensures no silent failures across your fan-out topology.

04

Confirm delivery

Data lands at every destination. stdout continues downstream for further processing. Append mode preserves historical state. Your pipeline is complete. Ship it.

0
+
Streams fan-out processed
0
countries
With active deployments
0
.99% uptime
Enterprise SLA guarantee
0
x faster
Than manual copy workflows
Case Study

How StreamVault Cut Pipeline Complexity by 74%

StreamVault processes 1.8 terabytes of telemetry data per hour across 12 data centers. Before FanOut, their engineering team maintained a brittle mesh of custom multiplexer scripts to route pipeline output to multiple log sinks, archive buckets, and real-time dashboards. Every new destination required a code change, a PR review, and a deploy cycle. "We were spending more time on plumbing than on product," said Kira Nakamura, VP of Platform Engineering.

"FanOut replaced 9,000 lines of custom routing code with a single operator. We went from a three-sprint integration to a one-line config change."

After deploying FanOut with --output-error=warn-nopipe across their ingestion tier, StreamVault reduced their pipeline failure rate by 91%. Append mode (-a) enabled safe concurrent writes to rotating log files without data loss. The team reclaimed two full engineering headcount that had been dedicated to pipeline maintenance. "FanOut isn't just a tool. It's the missing primitive," Nakamura added. "We should have had this from day one."

Pricing

Simple, transparent pricing

Start free. Scale without friction.

Starter
$0/month

For individual developers exploring fan-out.

  • 1 destination file per stream
  • stdout passthrough included
  • 100 fan-out operations/day
  • Community support
  • Append mode
  • Interrupt shielding
  • Output error policies
Get Started Free
Most Popular
Pro
$29/month

For teams that need reliable multi-destination fan-out.

  • Unlimited destination files
  • stdout passthrough included
  • Unlimited fan-out operations
  • Append mode (-a)
  • Interrupt shielding (-i)
  • Pipe diagnostics (-p)
  • Custom output-error policies
Start Pro Trial
Team
$79/seat/month

For orgs running fan-out at production scale.

  • Everything in Pro
  • All --output-error modes
  • warn / warn-nopipe / exit / exit-nopipe
  • SSO & RBAC
  • Audit logs
  • Shared pipeline templates
  • Priority support (4h SLA)
Start Team Trial
Enterprise
Custom

For organizations where fan-out is mission-critical infrastructure.

  • Everything in Team
  • Dedicated account engineer
  • Custom SLA (99.999%)
  • On-premise deployment
  • SOC 2 & HIPAA compliance
  • Unlimited seats
  • 24/7 support with war-room access
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What Teams Are Saying

Trusted by pipeline-first engineers

★★★★★

"We replaced our entire custom log multiplexer with FanOut. Append mode alone saved us 200 engineering hours per quarter. This is the primitive the ecosystem has been waiting for."

Simone Nakamura
Simone Nakamura VP of Platform Engineering, StreamVault
★★★★★

"The --output-error policy engine is genuinely best-in-class. We run warn-nopipe in production and exit in staging. Different failure semantics for different environments. High-leverage configuration."

Marcus Bell
Marcus Bell Staff SRE, InfraCo
★★★★★

"I was manually copying pipeline output between files. Then I found FanOut. One command, multiple destinations, zero overhead. It's one of those 'why didn't this exist before' products."

Felix Chen
Felix Chen Solo Developer & Indie Hacker
★★★★★

"The interrupt shielding feature is non-negotiable for our production pipelines. SIGINT used to corrupt mid-write log files. FanOut's -i flag eliminated that entire failure class."

Oscar Holt
Oscar Holt CTO, VectorOps
★★★★★

"We evaluated three fan-out solutions. FanOut was the only one with first-class pipe diagnostics. The -p flag gives us observability into write errors that we literally couldn't get anywhere else."

Rachel Park
Rachel Park Director of Data Infrastructure, NorthStar AI
See It Live

FanOut in action

Real commands. Real output. One stream, multiple destinations.

Basic Fan-Out 
$ echo "deploy: production v4.2.1 status=success" | fanout deploy.log
deploy: production v4.2.1 status=success

$ cat deploy.log
deploy: production v4.2.1 status=success
Multi-Destination Append 
$ echo "metric: cpu_usage=42%" | fanout -a metrics.log audit.log
metric: cpu_usage=42%

$ echo "metric: mem_usage=67%" | fanout -a metrics.log audit.log
metric: mem_usage=67%

$ cat metrics.log
metric: cpu_usage=42%
metric: mem_usage=67%
Pipeline Fan-Out with Interrupt Shield 
$ ls -1 /var/log/*.log | fanout -i -a filelist.txt | wc -l
12

$ head -3 filelist.txt
/var/log/auth.log
/var/log/kern.log
/var/log/syslog

Enterprise-Grade Security & Compliance

🔒
SOC 2 Type II
🏛️
ISO 27001
🇪🇺
GDPR
🏥
HIPAA
☁️
Cloud-Native
FAQ

Frequently asked questions

FanOut reads data from standard input and simultaneously writes it to standard output and one or more destination files. Think of it as a data splitter — one input stream, unlimited output destinations. It's the core primitive for any serious pipeline architecture.

Absolutely. FanOut processes data as a passthrough — we don't store, inspect, or modify your stream content. Combined with our SOC 2 Type II certification and interrupt shielding (-i), your data is protected end-to-end during every fan-out operation.

That's exactly what our Output Error Policy Engine is for. Choose from four modes: warn (diagnose but continue), warn-nopipe (warn only for non-pipe failures), exit (halt on any failure), or exit-nopipe (halt only for non-pipe failures). Default behavior diagnoses non-pipe errors and exits on pipe errors. Full control.

FanOut is infrastructure-layer software that operates directly on your data streams. It runs wherever your pipeline runs — air-gapped environments, edge deployments, submarines. No cloud dependency required for core fan-out operations.

FanOut is designed to be a composable primitive. It reads from stdin and writes to stdout, making it a first-class citizen in any pipeline. Slot it between any producer and consumer. Pipe in, fan out. It composes with every tool in your stack.

See mandō's portfolio

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