---
title: "Reading preview logs"
description: "Follow install, build, and boot logs to understand exactly what your preview is doing."
url: https://evonx.ai/docs/preview-and-debug/reading-logs
locale: en
updated: 2026-09-04
---

# Reading preview logs

Follow install, build, and boot logs to understand exactly what your preview is doing.

Every preview streams its logs live — the same output a developer would watch in a
terminal. You don't need to be one to get value from them: knowing the phases and
a few landmark lines tells you where a preview is, and where it got stuck.

## The phases of a preview boot

A starting preview walks through predictable stages, and the logs announce each:

1. **Install** — dependencies are restored ("Preview starting…", restore/install
   output). Slow the first time, fast after.
2. **Database preparation** (API previews) — an ephemeral Postgres is created,
   migrations run, seed data loads. See
   [Preview databases](/docs/preview-and-debug/preview-databases).
3. **Build** — the project compiles. Warnings are usually fine; errors stop the
   boot here.
4. **Boot** — the app starts and binds its port; the preview URL becomes active.

Once running, the logs switch to live application output: every request, and every
error, as it happens.

## How to read a failure

1. Scroll to the **first** error, not the last. Failures cascade; the earliest one
   is almost always the cause and the rest are noise.

2. Note the phase it happened in. A build error means the code doesn't compile; a
   database error during startup usually means migrations and schema disagree; an
   error after boot is an application bug.

3. Hand it off: [Analyse & Fix](/docs/preview-and-debug/analyse-and-fix) reads the
   same logs, identifies the root cause, and proposes the fix — you don't need to
   interpret the stack trace yourself.

> **Tip**
> Reproduce, then read. If the app misbehaves on a specific action, do the action
> while watching the log stream — the lines that appear at that moment are your
> suspects.

## Related

- [Troubleshoot previews](/docs/preview-and-debug/troubleshoot-previews) — common
  failures, symptom by symptom.
- [Preview Hub overview](/docs/preview-and-debug/preview-hub) — where the logs
  live.