devtools_har

HAR 1.2 and browser DevTools-extended typed models for Dart. Full coverage of log, entries, requests, responses, timings, cache, cookies, and vendor-prefixed fields.

Features

• Full HAR 1.2 coverage — typed Dart classes for every object in the HAR 1.2 spec: HarLog, HarEntry, HarRequest, HarResponse, HarCookie, HarHeader, HarQueryParam, HarPostData, HarContent, HarCache, HarTimings, and HarPage.

• Browser DevTools extensions — DevToolsHarEntry, DevToolsHarRequest, DevToolsHarResponse, DevToolsHarCookie, and DevToolsHarTimings extend the base models with underscore-prefixed fields emitted by Chromium-based DevTools when exporting HAR files (_initiator, _priority, _resourceType, _fromCache, _fromServiceWorker, _webSocketMessages, _sameSite, etc.).

• Lossless round-tripping — fromJson → toJson preserves the original document, including unknown custom fields (_-prefixed) via a generic custom map and raw-value fields such as expiresRaw.

• Numeric-type fidelity — whole-number doubles (common after JSON deserialization) are normalized to int so that 42.0 serializes as 42, matching the original HAR source.

• Null-policy control — toJson(includeNulls: true) emits every optional field for tooling that requires a complete schema; the default omits null values for compact output.

• Pure Dart, no dependencies — no Flutter SDK, no code generation, no dart:io / dart:html. Works on VM, Web, and ahead-of-time targets.

Getting started

dependencies:
  devtools_har: ^0.1.0

import 'package:devtools_har/devtools_har.dart';

Usage

Parse a HAR file

import 'dart:io';

import 'package:devtools_har/devtools_har.dart';

void main() {
  final jsonStr = File('network_log.har').readAsStringSync();
  final root = HarParser.parse(jsonStr);

  for (final entry in root.log.entries.take(3)) {
    print('${entry.request.method} ${entry.request.url} '
        '-> ${entry.response.status}');
  }
}

Parse browser DevTools HAR exports

import 'dart:io';

import 'package:devtools_har/devtools_har.dart';

final jsonStr = File('network_log.har').readAsStringSync();
final root = DevToolsHarParser.parse(jsonStr);

final entry = root.log.entries.first;
print(entry.request.url);
print(entry.timings.wait);
print(entry.priority);     // e.g. "High"
print(entry.resourceType); // e.g. "XHR"

Build and serialize

final entry = HarEntry(
  startedDateTime: DateTime.now().toUtc(),
  totalTime: 120,
  request: HarRequest(
    method: HttpMethod.get,
    url: Uri.parse('https://api.example.com/v1/vehicles'),
    httpVersion: 'HTTP/1.1',
    headers: [],
    queryString: [],
    headersSize: -1,
    bodySize: 0,
  ),
  response: HarResponse(
    status: 200,
    statusText: 'OK',
    httpVersion: 'HTTP/1.1',
    cookies: const [],
    headers: const [],
    content: const HarContent(
      size: 0,
      mimeType: HarContent.kFallbackMimeType,
    ),
    redirectURL: '',
    headersSize: -1,
    bodySize: 0,
  ),
  cache: const HarCache(),
  timings: const HarTimings(send: 0, wait: 0, receive: 0),
);

// Compact (omit nulls)
final compact = entry.toJson();

// Verbose (include all optional keys)
final verbose = entry.toJson(includeNulls: true);

Round-trip fidelity

import 'dart:convert';

final original = '{"name":"sid","value":"abc","expires":"Sun, 15 Jul 2012 ..."}';
final cookie = HarCookie.fromJson(jsonDecode(original));

// expiresRaw preserves the original string format
assert(jsonEncode(cookie.toJson()).contains('Sun, 15 Jul 2012'));

Architecture

The base models handle everything defined by the HAR 1.2 specification. The devtools/ layer extends each model with _-prefixed fields that browser DevTools add when exporting network logs. Both layers share the same fromJson / toJson contract and can be used interchangeably where only HAR 1.2 fields are needed.

Custom fields

All model classes carry a Map<String, Object?> custom property that collects any unknown _-prefixed keys found during parsing. These fields are re-emitted by toJson, ensuring vendor extensions survive a round-trip without data loss.

final entry = DevToolsHarEntry.fromJson(json);

// Access a recognized DevTools field
print(entry.priority);

// Access an unrecognized vendor field
print(entry.custom['_myToolAnnotation']);

References

• HAR 1.2 Specification
• Chromium DevTools Protocol — Network domain