Compress HEIC to 100KB or less.

Compressing an iPhone HEIC photo down to 100KB is one of the most common size targets people need online — and one of the most frustrating to hit by hand. Government portals, exam registration sites, visa applications, and job application systems routinely cap photo uploads at exactly 100KB and reject anything larger, often with no help on how to get there. This tool does exactly that: you type 100, and it returns a JPEG at or under 100KB, with no upload and no guesswork.

Why 100KB is the magic number for online forms

The 100KB limit is everywhere because it is a convenient ceiling for the servers behind online forms. A 100KB photo is small enough to store millions of, quick to upload on a slow mobile connection, and cheap to process. So form designers pick it as a hard cap and reject anything that crosses it.

The problem is that modern phones do not produce 100KB photos. An iPhone shooting in HEIC — the default since iOS 11 — produces a single photo that is typically 1 to 5 megabytes. A typical 12-megapixel iPhone photo lands around 1.5 to 3MB. That means hitting a 100KB target is a 15× to 40× reduction, and doing it by trial and error with a generic editor is tedious: change a setting, export, check the size, repeat.

This is the gap a purpose-built 100KB HEIC compressor fills. Instead of asking you for a quality setting you don’t care about, it asks for the one number the form cares about — the size in KB — and hits it directly.

Who needs a 100KB HEIC compressor

A 100KB photo target comes up across a surprisingly wide range of official and semi-official contexts:

• Government portals. Many national and local government services — tax filing, identity systems, benefit applications, permit requests — cap uploaded images at 100KB. If your photo is even 101KB, the upload is rejected.
• Exam registration. Standardized tests, professional certifications, and university entrance systems often require a candidate photo under 100KB so they can store and verify thousands of them cheaply.
• Visa and immigration applications. Visa forms frequently specify both a pixel size and a file-size ceiling, with 100KB being a common maximum for the uploaded headshot.
• Job applications. Applicant tracking systems and careers portals often cap the profile photo or scanned documents at 100KB to keep their storage costs predictable.
• Membership and licensing platforms. Professional bodies, licensing boards, and membership sites use the same kind of ceiling.

In every one of these, the requirement is the same: a JPEG, at or under a specific KB limit, ideally without the photo looking degraded. That is exactly what this tool produces.

How to compress HEIC to 100KB, step by step

Using the tool is intentionally simple — there is no account, no settings menu, and nothing to install.

1. Open the compressor on this page. The engine loads once, in your browser, the first time you visit.
2. Drop your HEIC photo into the box, or click to select it from your device. The moment you choose a file, the tool decodes it and shows you a preview — so you can confirm you picked the right photo before doing anything else. (Most browsers cannot display HEIC directly, so the tool decodes it for you.)
3. Set the target to 100KB. It is preset, but you can type any number.
4. Click Compress. The tool searches for the best result that fits under 100KB, usually within a second or two for a phone photo.
5. Compare the before and after. The original is shown next to the result so you can see exactly what changed.
6. Download the result. You get a JPEG file named with the target size, ready to upload to your form.

If the form later complains, or if you want a little safety margin, type a slightly lower number (say 95KB) and compress again. Some forms round up at the boundary, so landing a few KB under is safer than landing exactly on 100KB.

How the compression actually works

It helps to understand what the tool is doing, especially if you care about why the result still looks good. The compression runs in four stages, all inside your browser.

1. Decode the HEIC

HEIC is a container that stores image data compressed with HEVC (also called H.265). Browsers — except Safari — generally cannot render HEIC directly, which is why an <img> pointed at a raw HEIC file shows nothing. The tool uses a WebAssembly module to decode the HEIC into raw pixels, entirely on your device. No pixel data is ever sent anywhere.

2. Try the highest quality that fits

With raw pixels in hand, the tool encodes them to JPEG. JPEG lets you choose a quality level from 1 to 100 — higher quality looks better but produces a larger file. The tool performs a binary search across quality levels to find the highest quality that still fits under 100KB. A binary search is fast: rather than trying quality 50, then 51, then 52, it jumps to the middle, checks whether that fits, and narrows in within a handful of attempts.

3. Protect a quality floor before resizing

Here is the part that protects how your photo looks. Older “hit a target size” approaches kept lowering quality until the size fit — sometimes crushing quality down into the low teens, which produces visible blockiness and mosaic artifacts, especially around faces and skin. That is exactly what you do not want in an ID or passport-style photo.

This tool instead enforces a quality floor. It will only reduce quality so far — and if even that floor still exceeds 100KB at full resolution, it stops lowering quality and starts resizing instead. The principle is simple: trade pixels before you trade visible quality. A smaller but clean photo looks far better than a full-size but blocky one.

4. Resize with a high-quality filter, then retry

When a resize is needed, the tool uses a Lanczos resampling filter, which is a high-quality method for downscaling photographs — it preserves edges and fine detail far better than the faster bilinear filters many tools default to. After resizing, it repeats the quality search on the smaller image, and loops until it lands under 100KB. The result is a JPEG that fits the target, given the constraints of the source photo.

What to expect from a 100KB photo

A reasonable question is whether 100KB is enough for a photo to look acceptable. The honest answer: for a headshot or ID-style photo, 100KB is plenty, and the result will look clean; for a large, detailed scene like a full landscape, 100KB forces visible compression because there is simply more information than 100KB can hold.

A few practical expectations:

• Face clarity is prioritized. Because the tool holds a quality floor and resizes only as much as needed, a portrait or headshot at 100KB keeps faces and edges sharp rather than turning blocky.
• Some resolution reduction is normal. A 12-megapixel iPhone photo cannot fit into 100KB at full size without heavy artifacting, so the tool will usually shrink it — often to somewhere around 800–1200 pixels on the long edge for a typical portrait. That is more than enough for a form photo, which is usually displayed small.
• The output is a single JPEG. No animation, no transparency, no multi-frame HEIC sequences — just the still image, in the format forms expect.

If your photo looks too soft after compression, the most likely cause is that the source is a busy, detailed scene rather than a headshot. Cropping tightly to the subject first (in your phone’s editor) usually improves the result dramatically, because the tool then spends its 100KB budget on the part that matters.

How photo file sizes actually work

It helps to understand what determines a photo’s file size, because it sets realistic expectations for what 100KB can look like. A JPEG’s size in bytes comes from three things:

1. Pixel count (resolution). More pixels means more data to encode. A 12-megapixel photo has roughly four times as many pixels as a 3-megapixel one, so all else equal it produces a larger file.
2. Quality level. JPEG is lossy: a higher quality setting keeps more fine detail and produces a larger file; a lower quality discards detail for a smaller file.
3. Image complexity. A photo full of fine detail, noise, or busy texture compresses poorly (larger file at the same quality), while a smooth photo with flat areas like sky or a plain wall compresses well (smaller file at the same quality).

That third point is why two photos at the same resolution and quality can come out very different sizes, and it is also why cropping tightly to your subject helps: removing busy background detail lets the encoder spend its 100KB budget on the part that matters.

What 100KB actually buys you

For a clean headshot-style photo, 100KB of JPEG at a sensible quality corresponds to roughly 800 to 1200 pixels on the long edge — more than enough for a form photo that will be displayed at a small size. A detailed landscape, by contrast, needs far more than 100KB to avoid looking soft, because there is simply more information to store. This is why ID and portrait photos take to a 100KB target so well, while wide scenes resist it.

Why a target-KB tool beats a quality slider

A normal image editor asks you for a quality number and hands you whatever size results. That is backwards for forms: the form cares about the size, not the quality. A target-KB compressor inverts the question — you give the size, the tool finds a suitable quality that fits — which is exactly what a hard 100KB ceiling demands.

HEIC vs JPEG: why the output is JPEG

A common point of confusion is why a “HEIC compressor” outputs a JPEG. There are two reasons.

First, almost no online form accepts HEIC uploads. Forms expect JPEG or PNG. HEIC is an Apple-pushed format with uneven support outside the Apple ecosystem, and most government, exam, and corporate form systems reject it outright even if the browser could display it.

Second, JPEG is far better suited to hitting a small KB target cleanly. JPEG was designed for photographs and produces small files with good-looking results; the same photo as a PNG would be several times larger for no visible benefit. Since the whole point is to land at or under a size limit, JPEG is the right output.

So the conversion from HEIC to JPEG is not a side effect — it is the point. Your original HEIC is never modified or deleted; the tool produces a new JPEG alongside it.

Photo requirements by use case

Different forms specify different combinations of file size, pixel dimensions, and aspect ratio. The tool handles the file-size part directly; for the others, a small amount of prep in your phone’s photo editor helps.

• File size. Set the tool to a few KB under what the form states (e.g. 95KB for a 100KB limit) to be safe against rounding.
• Pixel dimensions. If a form specifies exact pixels (for example, a minimum or maximum width and height), crop or resize in your phone’s editor to that aspect ratio first, then compress. The tool preserves your image’s dimensions unless it must shrink them to hit the target.
• Aspect ratio. Many ID photos want a specific ratio (square, or a portrait ratio like 3:4 or 4:5). Crop to the required ratio before compressing so the final file is already the right shape.
• Color and background. Some forms want a white or light background. That is a capture-time concern, not a compression one.

Always double-check the exact requirements on the specific form you are filling out — they vary, and the form itself is the authority. The tool takes care of the single most common hard blocker, which is the file-size ceiling.

Passport, visa and ID photo guidance

Because the 100KB limit shows up so often for identity documents, here is practical guidance for getting a usable result in those cases specifically. (Always confirm exact specs on your specific form — they vary by country and issuer.)

Capture tips

• Even, diffuse lighting. Stand facing a window or in soft daylight; avoid harsh direct sun and overhead lights that cast shadows across the face.
• Plain background. A white or off-white wall is the most widely accepted background, and as a bonus it helps compression — flat areas encode efficiently.
• Neutral expression, facing the camera. Eyes open, mouth closed, looking straight ahead, which is the standard for ID photos.
• Fill the frame with the head. The face should occupy a good portion of the frame, giving the compressor useful pixels to work with instead of spending them on empty background.

Before you compress

• Crop to the required ratio. Use your phone’s editor to crop to the aspect ratio the form wants (see below), so the final file is already the right shape.
• Shoot HEIC or JPEG — either is fine. This tool takes HEIC directly, and HEIC preserves quality well before compression, so there is no need to convert beforehand.

After you compress

• Land a few KB under the limit. Compress to roughly 95KB for a 100KB form to be safe against rounding at the boundary.
• Check the preview. Confirm the face is sharp and the orientation looks right before you upload to the form.

Common aspect ratios and dimensions

ID and form photos use a small set of standard shapes. Crop to the right one before compressing:

• Square (1:1). Used by many web platforms and some ID systems.
• Portrait 3:4 or 4:5. Common for passport-style photos.
• 2×2 inch (square). The classic US passport photo size — roughly 600×600 pixels when digitized at 300 DPI.
• 35×45 mm (portrait). Used by many countries’ visa and ID photos — roughly 413×531 pixels at 300 DPI.

The tool itself does not enforce an aspect ratio; it preserves whatever you give it unless it must resize to hit the target, so set the ratio during cropping. The final pixel dimensions depend on how much the tool had to shrink to reach 100KB, but a tightly cropped headshot keeps more than enough pixels for any standard form.

Troubleshooting

The form still says the file is too large. Some forms count size slightly differently, or round up. Re-compress targeting a few KB lower (for example, 95KB or 90KB) and try again. The tool always lands at or under the number you type.

The form rejects the format. The output is a standard JPEG with a .jpg extension, which virtually every form accepts. If a form specifically wants .jpeg, renaming the extension works — the file contents are identical.

The photo won’t preview or compress. Make sure you are uploading an actual HEIC/HEIF file and not a screenshot or a file with a renamed extension. Very occasionally a HEIC from an unusual app or an interrupted transfer is incomplete; re-saving or re-exporting the original fixes it.

Compression feels slow. Large source files (multiple megabytes, or very high resolution) take longer because decoding and encoding scale with pixel count. This is normal and processing time varies with the device and pixel count. Everything happens on your device, so a slow connection does not slow it down.

The result looks too soft. Crop tightly to the subject first, so the tool spends its 100KB budget on what matters. A headshot cropped before compression always looks better at 100KB than a wide scene.

Privacy: nothing leaves your device

This deserves to be said plainly, because the photos people compress to 100KB — passport photos, ID images, exam portraits, visa headshots — are among the most sensitive files they handle.

Your image never leaves your device. There is no upload, no cloud processing, no server that sees your photo. The decoding and compression happen locally, inside your browser, using a WebAssembly module. When you close the tab, the data is gone. There is no account, no storage, and no analytics applied to your image.

This is a meaningful difference from most “online compressor” websites, which upload your photo to a server, process it there, and send it back. For a vacation photo that may not matter; for a passport or visa photo, it matters a great deal. Running everything locally is both a privacy guarantee and a speed advantage — there is no round trip to a server and back.

How this compares to other approaches

There are several common ways people try to hit a 100KB target, and each has trade-offs.

• A generic online compressor. These usually upload your photo, expose you to ads and tracking, and give you a quality slider rather than a target size — so you still have to guess and re-check. They also see your photo, which is a concern for sensitive images.
• A phone editor or photos app. Built-in editors can export HEIC as JPEG, but they don’t target a file size. You get whatever size the chosen quality produces, and you iterate manually until it happens to fit.
• Desktop image software. Powerful, but overkill for one photo, and usually not available on the phone where your HEIC lives.
• This tool. Purpose-built for the exact problem: type the KB target, get a JPEG that fits, locally and privately, with no setup.

The right tool depends on your situation, but for the specific job of “I have an iPhone photo and my form needs it under 100KB,” a targeted browser-side compressor is the most direct path.

Related target sizes

Not every form wants exactly 100KB. If your limit is different, the same tool hits any target:

• Need less? A 50KB HEIC compressor for the stricter forms that cap at half.
• Need more? A 200KB HEIC compressor for forms with a more generous ceiling — you’ll keep noticeably more resolution.
• This page. The 100KB target covered above, the most common ceiling of all.

Whatever number your form states, type it and the tool lands at or under it — privately, in your browser, with no upload.