Compare voltage to these popular alternatives based on real-world usage and developer feedback.

Sidekiq uses threads to handle many jobs at the same time in the same process. It does not require Rails but will integrate tightly with Rails 3/4 to make background processing dead simple.

It is an open-source framework that helps you to create, process and manage your background jobs, i.e. operations you don't want to put in your request processing pipeline. It supports all kind of background tasks – short-running and long-running, CPU intensive and I/O intensive, one shot and recurrent.

It is a free and open-source document converter, widely used as a writing tool and as a basis for publishing workflows. It converts files from one markup format into another. It can convert documents in (several dialects of) Markdown, reStructuredText, textile, HTML, DocBook, LaTeX, MediaWiki markup, TWiki and many more.

Background-only application which launches and runs other applications, or opens documents, at specified dates and times.

It is a simple typesetting application. Turn plain Markdown into a formatted PDF, ready for print. Focus on content, not formatting.

It is an alternative PHP FastCGI implementation with some additional features useful for sites of any size, especially busier sites. It includes Adaptive process spawning, Advanced process management with graceful stop/start, Emergency restart in case of accidental opcode cache destruction etc.

Background jobs can be any Ruby class or module that responds to perform. Your existing classes can easily be converted to background jobs or you can create new classes specifically to do work. Or, you can do both.

Beanstalks's interface is generic, but was originally designed for reducing the latency of page views in high-volume web applications by running time-consuming tasks asynchronously.

The fastest, most reliable, Redis-based queue for Node. Carefully written for rock solid stability and atomicity.

wkhtmltopdf and wkhtmltoimage are command line tools to render HTML into PDF and various image formats using the QT Webkit rendering engine. These run entirely "headless" and do not require a display or display service.

Delayed_job (or DJ) encapsulates the common pattern of asynchronously executing longer tasks in the background. It is a direct extraction from Shopify where the job table is responsible for a multitude of core tasks.

Kue is a feature rich priority job queue for node.js backed by redis. A key feature of Kue is its clean user-interface for viewing and managing queued, active, failed, and completed jobs.

It is a visual rendering engine for HTML and CSS that can export to PDF. It aims to support web standards for printing. It is free software made available under a BSD license.
DocRaptor makes it easy to convert HTML to PDF and XLS format. Choose your document format, select configuration options and make an HTTP POST request to our server. DocRaptor returns your file in a matter of seconds. We provide extensive documentation and examples to get you started, and our API makes it easy to use DocRaptor to generate PDF and Excel files in your own web applications.

Convert anything to anything - more than 200 different audio, video, document, ebook, archive, image, spreadsheet and presentation formats supported.

Que is a high-performance alternative to DelayedJob or QueueClassic that improves the reliability of your application by protecting your jobs with the same ACID guarantees as the rest of your data.

It is a suite of software based on an interpreter for Adobe Systems' PostScript and PDF page description languages. Its main purposes are the rasterization or rendering of such page description language files.

Docparser is a cloud based document processing solution and workflow automation software. Docparser makes it easy to convert PDF documents into structured data and automate document based workflows.

Redis -> Sidekiq == Faktory -> Faktory. Faktory is a server daemon which provides a simple API to produce and consume background jobs. Jobs are a small JSON hash with a few mandatory keys.

It is a simple, reliable & scalable background processing library for Clojure. It has a transparent design & cloud-native architecture.

It is a cross-platform Unix init scheme with service supervision, a replacement for sysvinit, and other init schemes. It runs on GNU/Linux, *BSD, MacOSX, Solaris, and can easily be adapted to other Unix operating systems.

It is a job queue for PostgreSQL running on Node.js. It allows you to run jobs (e.g. sending emails, performing calculations, generating PDFs, etc) "in the background" so that your HTTP response/application code is not held up. Can be used with any PostgreSQL-backed application. Pairs beautifully with PostGraphile or PostgREST.

It provides developers with a tool to convert their HTML documents to PDF with high-fidelity. Packages are available for Node.js, Python, and PHP and the API allows any programming languages to be used.

Mission-critical automation you can audit, control and run on-prem. No black boxes. No silent failures. No data leaks. Built for teams that cannot afford uncertainty.

Posthook provides an API for scheduling tasks at specific times where the only requirement is the ability to make and receive HTTPS requests.
PDFGate is a developer-focused PDF API for generating and managing PDFs from applications. It supports HTML-to-PDF conversion, fillable PDF form fields, and a growing set of PDF utilities designed for backend workflows. The API is built for reliability and precision, making it suitable for invoices, contracts, reports, and other transactional documents. PDFGate emphasizes modern API design, predictable rendering, and features often missing from simpler HTML-to-PDF services, such as native support for interactive form fields. It is designed for teams that need more than basic PDF generation, with a roadmap that includes digital signatures, SDKs, and additional PDF processing endpoints.

Creatoryn is a free web-based suite of image tools for format conversion, resizing, compression, and cropping. It supports bulk workflows and processes images locally in the browser (no cloud processing required).

Free cron expression translator for Unix and Quartz. Convert cron syntax to plain English with visual builder and multilingual support.

AI-powered OCR and document extraction API converts documents to structured JSON in seconds. 98%+ accuracy for invoices, Aadhaar, PAN, salary slips & 20+ document types. Pay per page.

Free online tools and developer APIs for PDF processing, image optimization, data formatting, and security tasks

Generate professional PDFs from HTML templates via API. Create invoices, reports, certificates and more with our fast, reliable PDF generation service.

Production-grade workflow automation. No drag-and-drop required. Build, version, and deploy your workflows with YAML.

Plan, write, and publish books, PDF guides, workbooks, and audiobooks with AI workflows. Customize branding and export instantly.

It is a background server process for processing messages from Google Pub/Sub. It was designed to be an efficient, configurable process that easily integrates into any ruby app.

It is a high-performance online file conversion and manipulation service for developers. It can be integrated into any application or platform in just a few minutes, scales up to handle any amount of traffic, uses little resources and supports 200+ conversion actions.

It is an XSLT processor for transforming XML documents into HTML, text, or other XML document types. It works with a compatible release of the Xerces-C++ XML parser: Xerces-C++ version 2.7.0. The focus for this release is on bug fixes, pluggable memory management, and enhanced stability improvements in stylesheet execution.

It makes it easier to understand the structure of JSON files. The output is valid JavaScript which can be used directly in code. It's very helpful when writing queries for tools like jq.

Workq is a job scheduling server strictly focused on simplifying job processing and streamlining coordination. It can run jobs in blocking foreground or non-blocking background mode.

Is a free online AI converter that transforms PNG to STL 3D files. Perfect for Image to 3D, Image to STL, 3MF to STL, OBJ to STL and STP File Viewer

Create stunning PPTs instantly with MagicSlides, the best AI PPT maker. Turn text, PDFs, YouTube, & URLs into ready-to-use presentations in 136+ languages.

Professional JSON tool with auto-fix, TypeScript/Python/Go code generation, SQL export, diff comparison, chart visualization, and schema validation. Free online JSON formatter and beautifier.

Boost productivity with WorkPPT's AI-powered tools: Summarize content, generate slides, chat with AI, merge/split PDFs, add stamps/watermarks, and convert files. Fast, secure, and user-friendly!

Resize and compress multiple images at once with ProBatchResizer. Free online batch image resizer for JPG, PNG, WEBP – Fast Secure Private featuring 130+ pre-build smart presets.

Instantly convert your photos to HD quality with the Upscayl AI Image Upscaler. This Upscayl Models enhances blurry, pixelated, or low-resolution photos to stunning 4K resolution in seconds — the Upscayl Image and Upscayl ai image upscaler you can rely on.

Convert fonts online free. 8 formats, 56 conversions: TTF to WOFF2, OTF to WOFF, and more. Auto CSS, batch processing, subsetting. Private, no signup.
Extract text from images and PDFs with 99.9% accuracy. Supports handwriting recognition and 100+ languages. No registration required. Best free AI-powered OCR solution.

A powerful image-to-table extraction utility. It allows developers to parse JPG/PNG images containing tabular data and convert them into machine-readable formats (Excel, CSV, JSON) for data processing pipelines.

Make image square, crop image to square, or resize image to square online free. Blur background, no crop. For Instagram, profiles, social media. No signup, no watermark.

Convert PNG images to SVG format instantly. Free online PNG to SVG converter. Remove backgrounds, resize, and create scalable vectors.